(svn r1834) - Fix: NPF does not check the owner of its target, busses try to enter other players' depots. TODO

- Add: asserts to find the v->u.rail.track == 0 problem.
- Add: IsValidDepot(), IsValidTown(), IsValidSign(), IsValidVehicle(), IsValidStation()
- Add: GetTileOwner(), IsTileOwner()
- Codechange: Replaced IsShipDepotTile(), IsTrainDepotTile(), IsRoadDepotTile() by IsTileDepotType().
- Codechange: typedeffed the MAP_OWNERS as Owner. Should be used as variable type.
- Codechange: Replaced a few uint by TileIndex.

depot.h

@@ -2,6 +2,7 @@
 #define DEPOT_H
 
 #include "pool.h"
+#include "tile.h"
 
 struct Depot {
 	TileIndex xy;
@@ -40,12 +41,39 @@ VARDEF TileIndex _last_built_road_depot_tile;
 VARDEF TileIndex _last_built_aircraft_depot_tile;
 VARDEF TileIndex _last_built_ship_depot_tile;
 
-bool IsTrainDepotTile(TileIndex tile);
-bool IsRoadDepotTile(TileIndex tile);
+/**
+ * Check if a depot really exists.
+ */
+static inline bool IsValidDepot(Depot* depot)
+{
+	return depot->xy != 0; /* XXX: Replace by INVALID_TILE someday */
+}
+
+/**
+ * Check if a tile is a depot of the given type.
+ */
+static inline bool IsTileDepotType(TileIndex tile, TransportType type)
+{
+	switch(type)
+	{
+		case TRANSPORT_RAIL:
+			return IsTileType(tile, MP_RAILWAY) && (_map5[tile] & 0xFC) == 0xC0;
+			break;
+		case TRANSPORT_ROAD:
+			return IsTileType(tile, MP_STREET) && (_map5[tile] & 0xF0) == 0x20;
+			break;
+		case TRANSPORT_WATER:
+			return IsTileType(tile, MP_WATER) && (_map5[tile] & ~3) == 0x80;
+			break;
+		default:
+			assert(0);
+			return false;
+	}
+}
+
 Depot *GetDepotByTile(uint tile);
 void InitializeDepot(void);
 Depot *AllocateDepot(void);
-bool IsShipDepotTile(TileIndex tile);
 void DoDeleteDepot(uint tile);
 
 #endif /* DEPOT_H */