Add the X11 fd to main input select() set, and call VO check_events() if
it becomes readable. Only done in vo xv code for now, though would make
sense for other X11-based VOs too.
git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@24153 b3059339-0415-0410-9bf9-f77b7e298cf2