-Change how Odamex sleeps until the next frame by calculating the milliseconds until the next frame should start and passing that amount to SDL_Delay instead of calling SDL_Delay(1) until the appropriate time.

git-svn-id: http://odamex.net/svn/root/trunk@3904 b0bcef46-2027-0410-bd56-ab726e9a1d04
-Import the vid_capfps cvar from the rend32 branch to allow uncapped (but not interpolated) framerates for testing purposes.

git-svn-id: http://odamex.net/svn/root/trunk@3905 b0bcef46-2027-0410-bd56-ab726e9a1d04