(svn r2391) - Feature: saving games happen in a seperate thread so you no longer will have to wait such a long time (especially handy on bigger maps and multiplayer games). The mouse also changes into the 'ZZZ' state :P. The thread on windows is currently given a little-bit-less-than-normal priority so it should not interfere that much with the gameplay; it will take a bit longer though. Upon the exit of the game any pending saves are waited upon.

- Fix: fixed GetSavegameFormat() so that it takes the best compressor (highest), or a forced one added with the parameter
- Open issues: 
1. Don't attempt to load a game while saving is in progress, it will kick you back to the intro-screen with only the vast ocean to look at.
2. The server is disabled from threaded-saving, but might be enabled in the future.
3. Current implementation only allows 1 additional running thread.
4. Stupid global variables.....grrr
Big thanks for TrueLight and the amazing memorypool :D

ttd.c

@@ -686,6 +686,7 @@ int ttd_main(int argc, char* argv[])
 
 	while (_video_driver->main_loop() == ML_SWITCHDRIVER) {}
 
+	JoinOTTDThread();
 	IConsoleFree();
 
 #ifdef ENABLE_NETWORK