libhb: handle incorrect stuffing in transport streams

Incorrectly formatted stuffing causes invalid PCRs which results in sync
issues.

I've only seen this in one poorly authored BD, but it's easy to handle.


git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@5152 b64f7644-9d1e-0410-96f1-a4d463321fa5