Megalux Frame demuxer
lavc/subviewerdec: fix potential NULL deref.

Fixes CID966647
lavfi/avfilter: remove now unused {src,cur,out}_buf.

This was supposed to be removed in 565e4993, but it was delayed due to
the port of the remaining filters. These buffer ref pointers are not
used anymore, thus dropped.
fate: kerndeint requires gpl
lavfi/kerndeint: get pix format description only once.

This makes the code faster.
vf_tinterlace: fix logical/bit op mixup

Fixes CID966642

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