(svn r5946) -Add: merged the TGP branch to mainline. TGP adds:

- New optional landscape generator (TerraGenesis Perlin)
  - Load heightmaps (either BMP or PNG)
  - Progress dialog while generating worlds (no longer a 'hanging' screen)
  - New dialogs for NewGame, Create Scenario and Play Heightmap
    - Easier to configure your landscape
    - More things to configure (tree-placer, ..)
  - Speedup of world generation
  - New console command 'restart': restart the map EXACTLY as it was when you
      first started it (needs a game made after or with this commit)
  - New console command 'getseed': get the seed of your map and share it with
      others (of course only works with generated maps)
  - Many new, world generation related, things
  - Many internal cleanups and rewrites
  Many tnx to those people who helped making this:
     Belugas, DaleStan, glx, KUDr, RichK67, Rubidium, and TrueLight (alfabetic)
  Many tnx to those who helped testing:
     Arnau, Bjarni, and tokai (alfabetic)
  And to all other people who helped testing and sending comments / bugs
  Stats: 673 lines changed, 3534 new lines, 79 new strings

thread.c

@@ -7,7 +7,7 @@
 #if defined(__AMIGA__) || defined(__MORPHOS__)
 OTTDThread* OTTDCreateThread(OTTDThreadFunc function, void* arg) { return NULL; }
 void* OTTDJoinThread(OTTDThread* t) { return NULL; }
-
+void OTTDExitThread() { NOT_REACHED(); };
 
 #elif defined(__OS2__)
 
@@ -57,6 +57,10 @@ void* OTTDJoinThread(OTTDThread* t)
 	return ret;
 }
 
+void OTTDExitThread(void)
+{
+	_endthread();
+}
 
 #elif defined(UNIX)
 
@@ -91,6 +95,10 @@ void* OTTDJoinThread(OTTDThread* t)
 	return ret;
 }
 
+void OTTDExitThread(void)
+{
+	pthread_exit(NULL);
+}
 
 #elif defined(WIN32)
 
@@ -141,4 +149,9 @@ void* OTTDJoinThread(OTTDThread* t)
 	free(t);
 	return ret;
 }
+
+void OTTDExitThread(void)
+{
+	ExitThread(0);
+}
 #endif