(svn r2635) Fix: [ntp/misc] Improve the old pathfinder. Changed it to A* instead of Dijkstra.

- Benchmark shows that NTP is now around 10x faster than NPF.
  - Made IsTunnelTile macro to determine if a tile is a tunnel.
  - Added some useful debugging functions for making tiles red / getting accurate timestamps.
  - Remove old depot finding algorithm.
  - Disable warning for signed/unsigned comparisons.

debug.c

@@ -15,6 +15,7 @@ int _debug_net_level;
 int _debug_spritecache_level;
 int _debug_oldloader_level;
 int _debug_pbs_level;
+int _debug_ntp_level;
 #ifdef GPMI
 int _debug_gpmi_level;
 #endif /* GPMI */
@@ -49,6 +50,7 @@ typedef struct DebugLevel {
 	DEBUG_LEVEL(spritecache),
 	DEBUG_LEVEL(oldloader),
 	DEBUG_LEVEL(pbs),
+	DEBUG_LEVEL(ntp),
 #ifdef GPMI
 	DEBUG_LEVEL(gpmi),
 #endif