(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)

misc.c

@@ -156,6 +156,7 @@ void CSleep(int milliseconds)
 }
 
 void InitializeVehicles(void);
+void InitializeDepot(void);
 void InitializeOrders(void);
 void InitializeClearLand(void);
 void InitializeRail(void);
@@ -216,6 +217,7 @@ void InitializeGame(uint log_x, uint log_y)
 	}
 
 	InitializeVehicles();
+	InitializeDepot();
 	InitializeOrders();
 
 	InitNewsItemStructs();