(svn r3730) Multistop modifications:

-Codechange: Completely rewritten the slot assignment system. It now consumes less CPU cycles and memory
-Codechange: Increased maximum number of roadstops to 16.
-Fix: Several conditions where a slot becomes unliked from a vehicle
-Codechange: ClearSlot now only takes one parameter, the vehicle
-Feature: Console command 'clearslots' to clear ALL currently assinged slots. debug usage only
-Feature: vehicles that cannot get a slot now wait on the road instead of planlessly blocking stops or circling around
-Codechange: Adjusted debug levels
TODO: Make the slot finder compatible with (a) pathfinder(s).

station.h

@@ -29,7 +29,7 @@ typedef enum RoadStopType {
 enum {
 	INVALID_STATION = 0xFFFF,
 	NUM_SLOTS = 2,
-	ROAD_STOP_LIMIT = 8,
+	ROAD_STOP_LIMIT = 16,
 };
 
 typedef uint16 StationID;
@@ -202,8 +202,9 @@ static inline RoadStopType GetRoadStopType(TileIndex tile)
 }
 
 RoadStop * GetPrimaryRoadStop(const Station *st, RoadStopType type);
+uint GetNumRoadStops(const Station* st, RoadStopType type);
 RoadStop * AllocateRoadStop( void );
-void ClearSlot(Vehicle *v, RoadStop *rs);
+void ClearSlot(Vehicle *v);
 
 static inline bool IsTrainStationTile(TileIndex tile)
 {