* commit '3176217c':
  h264: decouple h264_ps from the h264 decoder

Main changes:

- a local GetBitContext is created for the various
  ff_h264_decode_seq_parameter_set() attempts

- just like the old code, remove_sps() is adjusted so it doesn't remove
  the pps.

  Fixes decode with Ticket #631
  http://ffmpeg.org/pipermail/ffmpeg-user/attachments/20111108/dae58f17/attachment.mp4
  but see next point as well.

- ff_h264_update_thread_context() is updated to work even when SPS
  isn't set as it breaks current skip_frame code. This makes sure we
  can still decode the sample from ticket #631 without the need for
  -flags2 +chunks. (Thanks to Michael)

- keep {sps,pps}_ref pointers that stay alive even when the active
  pps/sps get removed from the available lists (patch by michaelni with
  additionnal frees in ff_h264_free_context() from mateo)

- added a check on sps in avpriv_h264_has_num_reorder_frames() to fix
  crashes with mpegts_with_dvbsubs.ts from Ticket #4074
  http://samples.ffmpeg.org/ffmpeg-bugs/trac/ticket4074/mpegts_with_dvbsubs.ts

- in h264_parser.c:h264_parse(), after the ff_h264_decode_extradata() is
  called, the pps and sps from the local parser context are updated with
  the pps and sps from the used h264context. This fixes fate-flv-demux.

- in h264_slice.c, "PPS changed between slices" error is not triggered
  anymore in one condition as it makes fate-h264-xavc-4389 fails with
  THREADS=N (Thanks to Michael)
Merged-by: Clément Bœsch <clement@stupeflix.com>
Merged-by: Michael Niedermayer <michael@niedermayer.cc>
Merged-by: Matthieu Bouron <matthieu.bouron@stupeflix.com>