avformat/bink: seek to first frame

Some rare bink files include unused bytes between the frame table index
and first frame data.

Fixes ticket #3266.

This patch has also been tested with non-seekable protocols.
Signed-off-by: Peter Ross <pross@xvid.org>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/bink.c

@@ -188,7 +188,7 @@ static int read_header(AVFormatContext *s)
                            keyframe ? AVINDEX_KEYFRAME : 0);
     }
 
-    avio_skip(pb, 4);
+    avio_seek(pb, vst->index_entries[0].pos, SEEK_SET);
 
     bink->current_track = -1;
     return 0;