(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.

variables.h

@@ -211,6 +211,8 @@ typedef struct Patches {
 	uint32 npf_rail_station_penalty; /* The penalty for station tiles */
 	uint32 npf_rail_slope_penalty; /* The penalty for sloping upwards */
 	uint32 npf_rail_curve_penalty; /* The penalty for curves */
+	uint32 npf_buoy_penalty; /* The penalty for going over (through) a buoy */
+	uint32 npf_water_curve_penalty; /* The penalty for curves */
 
 	bool population_in_label; // Show the population of a town in his label?
 } Patches;