Prefer libavformat musepack demuxer over internal one (which does not even support v8).

git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@26455 b3059339-0415-0410-9bf9-f77b7e298cf2

libmpdemux/demux_lavf.c

@@ -171,6 +171,8 @@ static const char *preferred_list[] = {
     "flv",
     "swf",
     "mov,mp4,m4a,3gp,3g2,mj2",
+    "mpc",
+    "mpc8",
     NULL
 };