(svn r6771) -Codechange: Replace two macros with functions. IS_HUMAN_PLAYER and
IS_INTERACTIVE_PLAYER

(svn r6407) -Fix: Check return values of DoCommand() with CmdFailed and that of DoCommandP
with a boolean type.

(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 r6280) -Codechange: Use the same naming for trains as for other vehicles:
CMD_SEND_TRAIN_TO_DEPOT instead of CMD_TRAIN_GOTO_DEPOT

(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 r6055) -Codechange: added GetXXXArraySize, which returns HighestID + 1 (or, will do that).
It isn't the best name, but we couldn't find any better.
This unifies the pool-system even more.

(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 r5975) -Cleanup: use ORIGINAL_BASE_YEAR & ORIGINAL_MAX_YEAR where the functions really depend on the original date format.
-Cleanup: use DAYS_TILL_ORIGINAL_BASE_YEAR where the date variables are in the old date format and conversions are needed.
-Cleanup: replace one (forgotten) instance of uint16 with Date.

(svn r5887) -Cleanup: move date related functions, defines and variables to date.[ch]
-Cleanup: fix whitespace related coding style issues in date.[ch]
-Cleanup: make original comments doxygen compatible and remove/change outdated comments

(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 r4911) -Fix (FS#156): The Ai no longer attempts to build signals under bridges.
NOTE 1: Remove/revert this for the bridge branch
NOTE 2: Bug displays fundamental flaw in command system:
If two commands, where command 2 depends on command 1, have
to be checked, all those checks need to be manual.
(like in this example, first build rail then build signal.
BuildSignal cannot be checked without DC_EXEC as the rail
isn't there yet)

(svn r4342) Change the first two parameters of commands - virtual pixel coordinates of the tile to operate on - to a TileIndex
Remove DoCommandByTile(), because now it does the same as DoCommand()

(svn r3857) Add and use GetBridgeRampDirection()
Note: This slightly changes the behavior of GetAnyRoadBits() to only return a road piece for the start of the bridge ramp instead of a full ROAD_[XY]

(svn r3677) Remove the FindLandscapeHeightByTile()s from the default AI.
The corresponding TileInfos look like global variables at the first glance, but always get written to before reading in each function they are used in.

(svn r3564) Several smaller changes:
- Don't treat non-booleans as booleans
- Reduce variable scope
- Bracing
- Use DeMorgan's law to make conditionals easier to read
- if cascade -> switch
- Replace some magic numbers by symbolic names
- Avoid assignments within other statements

(svn r3367) Unify the 4 distinct CMD_CHANGE_{AIRCRAFT,ROADVEH,SHIP,TRAIN}_SERVICE_INT commands into one CMD_CHANGE_SERVICE_INT command.
As side effect this is a
-Fix: The default AI tried to change the service intervals of vehicles via the CMD_CHANGE_TRAIN_SERVICE_INT command - regardless of the type of the vehicle - which of course failed for non-trains

(svn r3226) -Fix: GPMI implementation had minor glitches
-Fix: the AI speed control is done by the AI-core, individual AIs don't have to do it (so, AIs were delayed twice ;)
-Add: Support for AI-network-clients (an AI, connecting to a remote server)
-Fix: minor AI-core problems

(svn r3181) -Bracing
-Indentation
-Whitespace
-DeMorgan's Law
-Test with NULL or 0 for non-booleans
-'\0' instead of 0 for chars
-Remove redundantly redundant comments (like DoFoo(); // Do foo)
-Join multiple short lines with a single statement
-Split single lines with multiple statements
-Avoid assignments in if

(svn r3073) int/byte -> EngineID/PlayerID/VehicleID
0/-1 -> INVALID_ENGINE
0x10 -> OWNER_NONE

(svn r3058) The default AI may not build dual headed trains under certain circumstances.
Simplify this check by testing the rail vehicle info flags instead of passing a global variable around.
Note: This is not exactly the original behaviour, because the Lev4 was always allowed to be built, but i guess that was a glitch.

(svn r2951) - Fix: [ 1259345 ] Changing engine in netgame opens train window for everyone
- Add IsLocalPlayer() which substitutes _local_player == _current_player