Merge commit '73953df7'

* commit '73953df7':
  Replace av_malloc() and memset(0) by av_mallocz()

Conflicts:
	libavformat/matroskadec.c
	libavformat/rmdec.c
	libavformat/utils.c

No change, as none of the split malloc+memset existed in ffmpeg
Merged-by: Michael Niedermayer <michaelni@gmx.at>