avformat/rtsp: Use av_freep() to avoid leaving stale pointers in memory

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avfilter/vf_boxblur: generate supported pixfmt list instead of hardcoding

This adds support for several more >8bit planar formats

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