Parse matroska clusters incrementally as opposed to all at once.

While the patch is ugly, it prevents us from downloading the entire first cluster during the call to av_find_stream_info(). As a result, start up latency is greatly improved.

TEST=start up time, seeking, everything works

Review URL:

git-svn-id: 4ff67af0-8c30-449e-8e8b-ad334ec8d88c
1 file changed