JVET-P1019: Output layer set

  - Add Access Unit detection to support  multi-layer streams containing multiple pictures per AU.

Brian Heng authored 5 years ago and Karsten Suehring committed 5 years ago

  - Add picture header and related syntax changes.

 Includes decoder side checks that detects if disallowed NAL unit types are used in the bitstream. The implementation is aligned with the spec text in JVET-P2001-v11, apart from the check of prefix and suffix APS NAL units which should be added when prefix and suffix APS is implemented (JVET-P0588/JVET-P0452).

- don't add a layer id, if a single layer is encoded/decoded
- add the layer id before the last dot in the file name
- if no dot exists, append layer id to the file name

  - Unsafe use of reference picture PPS pointers.

  - Add macro for code changes.

- CVS to start with GDR

Software implementation for N0278:
1. Added VPS encoding in encoder
2. Add new project StreamMergeApp to N-to-1 bitstream merge
3. Changed decoder to support only decoding the specified layer stream