(svn r2255) - Fix: [ 9680363 ] [NPF] Broken buoy handling for ships

Buoys will now try to get within 3 tiles of a buoy instead of a the actual buoy tile. This gets ships to got past buoys in a realistic (IMO) way instead of barging right through them.
- Fix: [NPF] Trains get curves penalties sometimes even when the track is straight.
- Add: [NPF] Ships get a penalty for going over buoys now, so they will try to go around.
- Add: [NPF] Ships get a penalty for curves too, yay for straight lines.
- Add: TrackdirToTrack(), TrackToTrackdir(), IsDiagonalTrack() and IsDiagonalTrackdir() helper functions.
- Add: IsBuoy() and IsBuoyTile() helper functions.
- Codechange: Rearranged part of the control flow of ShipController(), removing a goto.

order_cmd.c

@@ -166,7 +166,7 @@ int32 CmdInsertOrder(int x, int y, uint32 flags, uint32 veh_sel, uint32 packed_o
 			st = GetStation(new_order.station);
 
 			if (!IsValidStation(st) ||
-					(st->airport_type != AT_OILRIG && !(st->had_vehicle_of_type & HVOT_BUOY) && !CheckOwnership(st->owner))) {
+					(st->airport_type != AT_OILRIG && !(IsBuoy(st)) && !CheckOwnership(st->owner))) {
 				return CMD_ERROR;
 			}