Preview 4 up for download

This update contains mostly speed improvements with some minor gameplay updates.  You'll notice pathfinding behaving differently than previous games (if you pay attention to that sort of thing), and in general I expect most computers to experience much better frame rates with higher unit counts.

In the near future I'll be putting up the source code for this project at http://code.google.com/p/dune2/.  My focus in life needs to turn now to personal and professional affairs for some time.  If any of you are brave enough souls to look at my hideous source code, feel free to take a shot at bringing networked multiplayer capabilities to life.  Otherwise, you might have to wait some months before I get the energy and willpower to return to this project.  Thanks to everyone following and especially to the contributors.

And let this serve as an early birthday present where applicable.  ;)