Since we detect full screen resolutions already, I suggest that we limit the
hard-coded listed windowed resolutions to 'supported' 4:3 ratios: 600x480 (vga),
800x600 (svga), 1024x768 (xga), 1280x960, 1400x1050 (sxga+)

It would be nice to put the discussion of how to get xinerama to work in the
README (my old feature request about this died with the tracker) I have
different monitor setup now, but at the time it was quite annoying to have the
game centered on the break in the two monitors.

Likewise the help text when -r99 is used needs to be updated.