SDL has a bug (at least on Windows) where SDL_CreateWindow() with
SDL_WINDOW_FULLSCREEN doesn't use the configured resolution (if it's
higher than the current desktop resolution).
Try to work around that - based on Yamagi Quake II code.
Also, if GLimp_Init() fails, the "safe mode" fallback is now in
windowed mode instead of fullscreen mode.
Editor also seems to start, didn't test much further.
Only tested 32bit Windows, I fear the editor code isn't 64bit clean..
I hope I haven't broken anything elsewhere..
