Add in the missing SDL2 conditional compilation symbol for the WindowsGL project.
Can't reference an unassigned local variable...
Merge pull request #64 from UnfinityGames/monogame-SDL2WindowsGLFix

Some fixes to get the WindowsGL project to compile on Windows.
Update SDL2# and Theoraplay# submodules
Merge pull request #3 from flibitijibibo/monogame-sdl2

Update branch with current upstream changes.