- To reliably find audio in 720p or 1080i TS streams we need to search through first...

 - To reliably find audio in 720p or 1080i TS streams we need to search through first 50MB of file looking for the stream rather than first 18MB.
 - When we're looking for a PES header for some PID, check both that the TS 'start' bit is set and that the first 3 data bytes are an MPEG start code (the start bit may get set by an error not caught by the CRC).
 - Print the substream id when we reject a PID as "not audio" so we'll be able to debug TS streams using non-standard PES encapsulations.

git-svn-id: svn://svn.handbrake.fr/HandBrake/trunk@1642 b64f7644-9d1e-0410-96f1-a4d463321fa5