Ensure all SDL putenv calls are called before SDL_Init, otherwise it always defaults to windib and we lose functionality. || Let setmodeneeded=true be enough to get a screen resolution update.  This allows setting vid_vsync without needing to change resolution or restart.

git-svn-id: http://odamex.net/svn/root/trunk@5163 b0bcef46-2027-0410-bd56-ab726e9a1d04