Merge remote-tracking branch 'cehoyos/master'

* cehoyos/master:
  lavc/qdrw: Do not fail decoding valid Quickdraw images.
  lavf/mov: Use AVCOL_SPC constants when checking color_space.
  lavf/mov: Write colour matrix "6" for color_space bt470bg.
  lavf/mkv: Only skip prores header if the packet is large enough.

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