Cleanup cruft and obsolete files

This is a big "throw out crap and rearrange stuff" pull request.  If you don't like everything done here, feel free to request changes.

You should build this project from xcode.  I removed sdl_winmain from the xcode project (for the same reason there aren't any objective C files in the visual studio projects), but I don't have a mac and am relying on the fact that xcode project files look easy to read and modify by hand.

As for the changes, the commit messages are pretty self-explanatory (the first one breaks down the big changes).