(svn r7565) -Codechange: Rework DEBUG functionality. Look for appropiate debugging levels to
use in debug.h. grfmsg() is now used as a specific debug-function for grf.

(svn r6408) -Fix(r6406): compilation was broken
-Codechange: Rename TileIndexDiffCByDir to TileIndexDiffCByDiagDir because it accepts DiagDirections

(svn r6406) -Codechange: Rename TileOffsByDir to TileOffsByDiagDir because it accepts
DiagDirections, and add TileOffsByDir that handles Directions.
-Codechange: Make the treeloop use TileOffsByDir().

(svn r6353) -Codechange: Make DestinationID a typedef of uin16, which is as large as any type of destinataion (StationID, DepotID, WaypointID) it can hold
DestinationID being a union of these types is just hassle without benefit and cannot be handled correctly everywhere because of local lack of information

(svn r6142) -Codechange: added WaypointID (sorry DV, couldn't splits it anymore)
-Codechange: introduced DestinationID, which is in fact an union of several types
Used in Order struct, so no longer StationID is abused for all targets.
Hangars are a big exception, as they use a station-id with GOTO_DEPOT (go figure)

(svn r6047) -Codechange: FOR_ALL now _only_ loops valid items, and skips invalid ones
-Codechange: use IsValidXXX where ever possible
Note: both changes to prepare for new pool system, which needs those changes.
For every pool there are 2 ugly lines, which will be removed when done
implementing new pool system.
Based on FS#13 by blathijs, partly implemented.

(svn r5070) Merged the bridge branch
-Feature: Bridges can now be placed above:
Any railway track combination (excluding depots and waypoints)
Any road combination (excluding depots)
Clear tiles (duh), including fields
Tunnel entrances
Bridge heads

Thanks to Tron for idea and implementation, KUDr for the yapf synchronization and many others for hours of testing

There are still a number of visual problems remaining, especially when electric railways are on or under the bridge.
DO NOT REPORT THOSE BUGS FOR THE TIME BEING please.

(svn r4387) -Codechange: Use map accessors even for debugging purposes (npf).
-Codechange: Removed unused code from NPF

(svn r3472) - [PBS] Remove from trunk. Anyone interested can still find it in branch/pbs. This reverts revisions r3158, r3140, r3075, r2977, r2674, r2625, r2621, r2529, r2528, r2525, r2524, r2519, r2517, r2516, r2507, r2499. (in conjunction with Tron)
- The only change is that the nsignalsw.grf file is kept and that existing nightlies with PBS signals get those signals converted to combo-signals.

(svn r2929) * Move DistanceTrack from map.c to npf.c and rename to NPFDistanceTrack.
* Make NPFDistanceTrack return the distance multiplied by NPF_TILE_LENGTH to prevent rounding
This should make ship and train pathfinding more accurate and faster.
* Update IsEndOfLine to prevent trains from trying to go off a slope onto a tunnel entrance.

(svn r2625) - Fix: [pbs] Store the end of a train's reserved path explicitly. Prevents trains from unreserving eachothers paths in some cases.
- CodeChange: Use the TrackdirToTrack function instead of &7, and remove an unneeded variable.

(svn r2516) - Feature: [pbs] Implement path-based-signalling. This allows multiple trains within the same signal block, provided their paths dont intersect. For this the block must have all exit and entry signals be pbs signals. Place these by ctrl-clicking 4 times on a normal signal.
- Feature: [pbs] Implement autoplacement of pbs blocks, when a block has an entry and an exit pbs signal, covert the entire block to pbs. Can be turned off in the patch settings.
- Feature: [pbs] Allow showing of reserved status by making the tracks darker, when the pbs debug level is at least 1.

(svn r2514) - Codechange: [NPF] Move the checking of railtype into a funciton IsCompatibleRail().
- Codechange: [NPF] Check the railtype along a route against the engine type instead of against the previouse tile. This clears the way for electriefied rails.
- Add: [NPF] [ 1209644 ] A penalty for crossings (peter1138)

(svn r2473) - Add: VehicleMayEnterTile(), which checks if the tile owner of a tile is correct for a vehicle to enter it. Based upon glx's code.
- Fix: [ 1203769 ] [NPF] NPF tries to plan over bridges, through tunnels, over level crossings of other players. (glx)
- Codechange: Renamed TRANSPORT_MAX to TRANSPORT_END and added INVALID_TRANSPORT.
- Codechange: Moved IsLevelCrossing() from tile.h to rail.h
- Add: GetCrossingTransportType(), which returns the transport type (road, rail) of both tracks on a level crossing.
- Removed old TODO that was fulfilled already.

(svn r2456) * Prettyfied npf.c using enums and wrappers from rail.h.
* Moved GetTileRailType() from npf.c to rail.[ch].

(svn r2450) * Codechange: Replaced all uses of the arrays in tile.h with calls to the associated wrapper functions.
* Codechange: Made npf.c use some map array accessing wrappers instead of direct access.
* Codechange/Fix: Named every enum in tile.h. Fixes a nasty bug on MSVC where arrays would be initialised with zeroes (tnx Asterix_)
* Removed magic numbers from tables in tile.c.
* Added some explicit casts in tile.h.

(svn r2448) General cleanup of rail related code, more to follow.
* Add: rail.[ch] for rail-related enums and wrapper functions.
* Codechange: Removed dozens of magic numbers with below enums.
* Codechange: Rewrote CheckTrackCombination().
* Add: TILE_SIZE, TILE_PIXELS and TILE_HEIGHT constants.
* Add: enums RailTileType, RailTileSubtype, SignalType to mask against the map arrays.
* Add: enums Track, TrackBits, Trackdir, TrackdirBits for railway track data. (Note that the old RAIL_BIT constants are replaced by TRACK_BIT ones).
* Add: enums Direction and DiagDirection
* Codechange: Moved a bunch of track(dir) related lookup arrays from npf.[ch] to rail.[ch].
* Codechange: move RailType enum from tile.h to rail.h.
* Add: Wrapper functions for masking signal status in the map arrays: SignalAlongTrackdir, SignalAgainstTrackdir and SignalOnTrack.
* Add: Wrapper functions to access rail tiles, using above enums
* Add: Wrapper functions to modify tracks, trackdirs, directions, etc.
* Add: Wrapper functions for all lookup arrays in rail.[ch] (Arrays are still used in parts of the code)
* Codechange: Renamed some variables and arguments to better represent what they contain (railbit -> track, bits -> trackdirbits, etc.).
* Codechange: Don't use FindLandscapeHeight() in CmdRemoveSingleRail(), since it returns way too much info. Use GetTileSlope() instead.
* Codechange: [NPF] Removed some unused globals and code from npf.c.

(svn r2281) - Fix: [ 1115204 ] [NPF] When pressing the goto depot button, trains will now also look behind it if there is no depot in front. If so, the train reverses immediately. This also work anywhere, not just at stations.
- Add: [NPF] Reversing inside of depots now has a penalty. It also applies to trains only, other vehicles shouldn't bother reversing.
- Fix: [NPF] When checking whether to reverse a train, the trackdir of the first loc was used instead of the last vehicle as a starting node for pathfindig.
This might have caused some trains not reversing when they should have (or vice versa). Typo introduced when converting to GetVehicleTrackdir() in r2256.
- CodeChange: [NPF] Removed duplicate code by letting NPFRouteTjoStationOrTile() call NPFRouteToStationOrTileTwoWay().
- Add: [NPF] NPFRouteToDepotBreadthFirstTwoWay() to find a depot while also looking backwards.
- Add: It is now possibly to specify a path cost for aystar starting nodes.

(svn r2257) - Fix: [NPF] NPF debug markings modify _map2 instead of _map3_hi for street tiles, corrupting them.
Some info got moved around in r1768 for street tiles, but NPF did not get updated.

(svn r2255) - Fix: [ 9680363 ] [NPF] Broken buoy handling for ships
Buoys will now try to get within 3 tiles of a buoy instead of a the actual buoy tile. This gets ships to got past buoys in a realistic (IMO) way instead of barging right through them.
- Fix: [NPF] Trains get curves penalties sometimes even when the track is straight.
- Add: [NPF] Ships get a penalty for going over buoys now, so they will try to go around.
- Add: [NPF] Ships get a penalty for curves too, yay for straight lines.
- Add: TrackdirToTrack(), TrackToTrackdir(), IsDiagonalTrack() and IsDiagonalTrackdir() helper functions.
- Add: IsBuoy() and IsBuoyTile() helper functions.
- Codechange: Rearranged part of the control flow of ShipController(), removing a goto.

(svn r2182) - Add: [NPF] There is now a debug class for NPF. Use -d npf<level> to enable debugging printouts from npf.
- Codechange: [NPF] Removed NPF_MARKROUTE macro, to mark routes just specify a npf debugging level >= 1 on the commandline.

(svn r2181) - Add: DistanceTrack() to calculate the distance over optimally laid out tracks.
- Codechange: [NPF] Removed unused heuristic function NPFCalcTileHeuristic().
- Codechange: [NPF] Use DistanceTrack() instead of DistanceManhattan() for ship and train heuristic.
- Codechange: Renamed variables x and y to dx and dy in some of the distance calculation functions.

(svn r2165) - Codechange: [NPF] Properly enummed NPF hash size, it is easily changable now.
- Codechange: [NPF] Improved the NPF hash calculation slightly.
- Codechange: [NPF] Increased hash size, should speed up somewhat.

(svn r2159) - Fix: [NPF] Road vehicles never found their target station or depots (introduced in r2154)
- Fix: [NPF] Trains still tried to go through the back of depots.

(svn r2154) - Fix: [NPF] Vehicles should no longer try to drive through the back of depots and road stations.
- Add: GetDepotDirection() wrapper function.
- Fix: [NPF] Ships can now actually reach buoys.

(svn r2007) - Fix: [NPF] Slope penalties did not work correctly with foundations. (HackyKid)
- Fix: [NPF] Stations penalties were not applied correctly, since stations had no base cost. (HackyKid)
- Fix: [NPF] Lastred penalty was applied multiple times for every red signal, instead of just the last one. (HackyKid)

(svn r1963) - Add: [NPF] Penalty for a red signal that is the last signal on the path.
- Add: [NPF] NPFGetFlag() and NPFSetFlag() to wrap NPF node flag handling

(svn r1834) - Fix: NPF does not check the owner of its target, busses try to enter other players' depots. TODO
- Add: asserts to find the v->u.rail.track == 0 problem.
- Add: IsValidDepot(), IsValidTown(), IsValidSign(), IsValidVehicle(), IsValidStation()
- Add: GetTileOwner(), IsTileOwner()
- Codechange: Replaced IsShipDepotTile(), IsTrainDepotTile(), IsRoadDepotTile() by IsTileDepotType().
- Codechange: typedeffed the MAP_OWNERS as Owner. Should be used as variable type.
- Codechange: Replaced a few uint by TileIndex.

(svn r1817) -Codechange: Moved depot-functions to depot.c
-Codechange: Added wrappers around depot-access (GetDepot no exists)
-Codechange: Made depot-functions a bit more logic (no longer
GetDepotByTile crashes your game when you request it on a non-depot tile)
-Add: made depots dynamic (yes, 64k depots are possible now)

(svn r1751) - Feature: New PathFinder (NPF).
- Supports trains, road vehicles and ships.
- Uses A* pathfinding (same codebase as the new ai).
- Currently unlimited search depth, so might perform badly on large maps/networks (especially ships).
- Will always find a route if there is one.
- Allows custom penalties for obstacles to be set in openttd.cfg (npf_ values).
- With NPF enabled, ships can have orders that are very far apart. Be careful, this will break (ships get lost) when the old pathfinder is used again.
- Feature: Disabling 90 degree turns for trains and ships.
- Requires NPF to be enabled.
- Ships and trains can no longer make weird 90 degree turns on tile borders.
- Codechange: Removed table/directions.h.
- table/directions.h contained ugly static tables but was included more than once. The tables, along with a few new ones are in npf.[ch] now. Better suggestions for a location?
- Fix: Binary heap in queue.c did not allocate enough space, resulting in a segfault.
- Codechange: Rewritten FindFirstBit2x64, added KillFirstBit2x64.
- Codechange: Introduced constant INVALID_TILE, to replace the usage of 0 as an invalid tile. Also replaces TILE_WRAPPED.
- Codechange: Moved TileAddWrap() to map.[ch]
- Add TileIndexDiffCByDir(), TileIndexDiffCByDir().
- Codechange: Moved IsTrainStationTile() to station.h
- Add: IsRoadStationTile() and GetRoadStationDir().