libhb: simplify avcodec extradata parsing
Use avcodec parser->split() instead of writing our own parser.  This
makes extradata parsing work for stream formats other than vc1 if the 
need should ever arise.


git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@6429 b64f7644-9d1e-0410-96f1-a4d463321fa5