This allows all SDL code to take advantage of the atomic intrinsics on Windows, but doesn't cause applications just including SDL.h to pull in windows.h

Changed the CAS return value to bool, so it's efficient with OSAtomicCompareAndSwap32Barrier()
Added an atomic test adapted from code by Michael Davidsaver

Implemented SDL_SetWindowTitle(), which turned out to be fairly complex

* Formalized the interface with Java methods in SDL_android.h
* We don't need the feature system, at least right now
* Fixed waiting for the SDLMain thread