If user did not specify driver directly, all available
drivers will be probed (in order: v4l2,v4l1,bsdbt848,dummy).
In most cases first probed driver will be successfully autodetected
and used.
Autodetection will be disabled if user specified driver directly (in
command line or config).
git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@24423 b3059339-0415-0410-9bf9-f77b7e298cf2