avoid using deprecated reference_dts
muticat_probe: don't use null systime
cosmetics
pes_decaps: allow null length
express RAP relatively to CR
uref_stream: fix imprecision in RAP handling
better RAP handling + fix h264 init bug
fix unit test
Merge https://github.com/cmassiot/upipe

Conflicts:
	lib/upipe-av/upipe_avformat_source.c
Current state of bmdsink