vf_yadif: switch to an AVOptions-based system.
Merge commit '7536c671040f1f3ebc9f0d3b7831dac71436b775'

* commit '7536c671040f1f3ebc9f0d3b7831dac71436b775':
  vf_yadif: switch to an AVOptions-based system.

Conflicts:
	doc/filters.texi
	libavfilter/vf_yadif.c
	libavfilter/yadif.h

Merged-by: Michael Niedermayer <michaelni@gmx.at>
lavfi/blend: switch to AVOption-based system
lavfi/afade: switch to AVOption-base system