23 hours later, SDL is finally decoupled

It took me 23 hours worth of development work (which is a LOT for a hobby task) but I'm finally done decoupling SDL. The resulting product is much improved and much more modular. Future ports to other platforms (GP2X, Android, etc) are now much more doable.

Now that I've finished that task, and gotten almost all of the unit tests passing on Beagleboard (yes, you heard that correctly), I've realized that my current priorities should be working on the rev 2 PCB design (since it takes time to get it back from the manufacturer) and preparing for my CAX presentation (since that is the only thing that has a due date right now). After that, my next priority will be debugging the AVR code that Warren has been testing.