avfilter/vf_removelogo: use av_freep() for saftey

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avfilter/vf_removelogo: fix offset for accessing pixels above and below

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avfilter/vf_removelogo: fix pixel pointer so it points where its intended

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avfilter/lavfutils: fix memleak of avpacket

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