vf_yadif: factorize initializing the filtering callbacks

Do it all in config_props().
vf_yadif: fix out-of line reads

Some changes in the border pixels, visually indistinguishable.
Merge commit 'ccd70d9c1689990e5aef2de383199bbc7cf60d13'

* commit 'ccd70d9c1689990e5aef2de383199bbc7cf60d13':
  vf_yadif: factorize initializing the filtering callbacks

Conflicts:
	libavfilter/vf_yadif.c

Merged-by: Michael Niedermayer <michaelni@gmx.at>
Merge commit '64ed397635ef2666b0ca0c8d8c60a8bc44581d82'

* commit '64ed397635ef2666b0ca0c8d8c60a8bc44581d82':
  vf_yadif: fix out-of line reads

Conflicts:
	libavfilter/vf_yadif.c
	tests/ref/fate/filter-yadif-mode0
	tests/ref/fate/filter-yadif-mode1

Merged-by: Michael Niedermayer <michaelni@gmx.at>
mpegvideo_enc: draw edges on input

Improves Motion estimation, avoids using out of picture areas for %16 != 0

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