(svn r7195) -Feature: [FS#297, optional elrails] New patches/vehicles option 'disable electrified railways'.
(original patch by maedhros, ideas: peter1138, Darkvater, Rubidium, Patrick, Eddi|zuHause, ..)

(svn r7028) -Fix [FS#200]: Scenario bridges/tunnels cannot be demolished; now it's possible to
delete tunnels/bridges owned by nobody.

(svn r6776) -Codechange: Use IsValidPlayer() function to determine of a PlayerID is an
actual playable player (< MAX_PLAYERS) or not.

(svn r6775) -Codechange: Use some more proper types, especially Owner and PlayerID as
these are used intermixed often.

(svn r6774) -Codechange: Rename the badly named OWNER_SPECTATOR to PLAYER_SPECTATOR and
put it into player.h where it belongs (instead of map.h)

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

(svn r6381) -Cleanup: make the '/* */' comments that span multiple lines more uniform.
-Cleanup: whitespace alignment of a few tables.

(svn r5926) -Codechange: make _cur_year contain the full year, instead of the offset since 1920
-Codechange: store all year related variables that are _not_ stored in a savegame/transported over the network in the same format as _cur_year

(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-Cleanup: make original comments doxygen compatible and remove/change outdated comments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 r5315) -Fix: Prohibit altering a road tile while road works are in progress
This fixes some glitches like "turning" the excavation by adding/removing road bits or removing the road piece

(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 r4572) Remove vehicle_leave_tile_proc
There's exactly one implemented function (unbarring a level crossing) and one place where it can be triggered (a train leaves a level crossing)
It's a bit overkill, so just handle this one case where it can happen

(svn r4373) Rewrite GetSlopeZ_TunnelBridge() and slightly change its behavior:
- Report the correct z alongside the ramp when a foundation is present
- Always report the z under the bridge for a bridge middle part, except if the z hack is used
This should fix some weird behavior of the tile selector near bridges

(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 r3837) Partially unmagicfy restoring the tiles when deleting a bridge
Existing bug: When restoring a road piece which belongs to a town the town index unconditionally gets set to 0