matroskadec: read the CodecDelay element
Merge commit 'eb3b5501e8b85bfea09d533314cb6920efc42639'

* commit 'eb3b5501e8b85bfea09d533314cb6920efc42639':
  matroskadec: read the CodecDelay element

Conflicts:
	libavformat/matroska.h
	libavformat/matroskadec.c

See: d6f86d74edfa6e1464ddc613726559269bf1dc7b
Merged-by: Michael Niedermayer <michaelni@gmx.at>
avformat/avidec: set average frame rate from header

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