Almost all of them had their guts removed and replaced by libavfilter
long ago, but remove them anyway. They're pointless and have been
scheduled for deprecation.
Still leave vf_format (because we need it in some form) and vf_sub (not
sure).
This will break some builtin functionality: lavfi yadif defaults are
different, auto rotation and stereo3d downconversion are broken. These
might be fixed later.
wm4
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