(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)

road_cmd.c

@@ -11,6 +11,7 @@
 #include "gfx.h"
 #include "npf.h"
 #include "sound.h"
+#include "depot.h"
 
 /* When true, GetTrackStatus for roads will treat roads under reconstruction
  * as normal roads instead of impassable. This is used when detecting whether
@@ -116,12 +117,6 @@ static bool CheckAllowRemoveRoad(uint tile, uint br, bool *edge_road)
 	return true;
 }
 
-bool IsRoadDepotTile(TileIndex tile)
-{
-	return IsTileType(tile, MP_STREET) &&
-					(_map5[tile] & 0xF0) == 0x20;
-}
-
 uint GetRoadBitsByTile(TileIndex tile)
 {
 	uint32 r = GetTileTrackStatus(tile, TRANSPORT_ROAD);