avfilter/vf_hqdn3: use av_malloc_array()

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avfilter/vf_removelogo: use av_malloc_array()

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
Merge pull request #1 from FFmpeg/master

sync the code