Merge of r4383, r4403:

MP4 fixes:

*) Fixed mp4 if first entry in stsc was skipped (ticket #72).

   If first entry in stsc atom was skipped, and seek was to chunk
   boundary, than first_chunk in the generated stsc table wasn't
   set to 1.

*) Fixed handling of mp4 above 2G and 32bit offsets (ticket #84).