Change: Store station blocked/wires/pylons flags in map. (#11337)

This stores three flags in unused map bits, and avoids having to look up
station graphics and custom station specs to determine blocked/wires/pylons
status.

This potentially affects rail pathfinding performance.

Savegame version is not bumped, as the flags can just be updated every
time.

src/station_func.h

@@ -43,12 +43,6 @@ void UpdateStationDockingTiles(Station *st);
 void RemoveDockingTile(TileIndex t);
 void ClearDockingTilesCheckingNeighbours(TileIndex tile);
 
-/* Check if a rail station tile is traversable. */
-bool IsStationTileBlocked(TileIndex tile);
-
-bool CanStationTileHavePylons(TileIndex tile);
-bool CanStationTileHaveWires(TileIndex tile);
-
 void UpdateAirportsNoise();
 
 bool SplitGroundSpriteForOverlay(const TileInfo *ti, SpriteID *ground, RailTrackOffset *overlay_offset);