Fix potential endless loop while probing.

git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@36542 b3059339-0415-0410-9bf9-f77b7e298cf2
Only detect a file as MPEG-PS if we can find at least 2 packets.

git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@36543 b3059339-0415-0410-9bf9-f77b7e298cf2