Merge remote-tracking branch 'qatar/master'

* qatar/master:
  prores: get correct size for coded V plane if alpha is present
  prores: do not set pixel format on codec init
  pthread: prevent updating AVCodecContext from itself in frame_thread_free
  pthread: copy coded frame dimensions in update_context_from_thread
  vp8: prevent read from uninitialized memory in decode_mvs
  vp8: force reallocation in update_thread_context after frame size change
  vp8: fix return value if update_dimensions fails
  matroskadec: fix out of bounds write
  adpcmdec: calculate actual number of output samples for each decoder.
  adpcmdec: check remaining buffer size before decoding next block in the ADPCM IMA WAV decoder.
  adpcmdec: do not terminate early in ADPCM IMA Duck DK3 decoder.
  adpcmdec: remove unneeded buf_size==0 check.
  adpcmdec: remove unneeded zeroing of *data_size
  dnxhdenc: fixed signed multiplication overflow

Conflicts:
	tests/ref/fate/prores-alpha
	tests/ref/fate/truemotion1-24

Merged-by: Michael Niedermayer <michaelni@gmx.at>