af_resample: switch to an AVOptions-based system.
buffersrc: switch to an AVOptions-based system.
af_aformat: switch to an AVOptions-based system.
vf_(no)format: switch to an AVOptions-based system.
vf_aspect: switch to an AVOptions-based system.
vf_blackframe: switch to an AVOptions-based system.
Merge commit '4fa1f52e33b70029e2b621852f3af7c1ef9aecff'

* commit '4fa1f52e33b70029e2b621852f3af7c1ef9aecff':
  af_resample: switch to an AVOptions-based system.

Conflicts:
	libavfilter/avfilter.c

Merged-by: Michael Niedermayer <michaelni@gmx.at>
Merge commit 'd28cb849899abd98bf2dd72f5a3dd56d441aeb27'

* commit 'd28cb849899abd98bf2dd72f5a3dd56d441aeb27':
  buffersrc: switch to an AVOptions-based system.

Conflicts:
	doc/filters.texi
	libavfilter/buffersrc.c

Commit not merged, merge left to maintainer.

Merged-by: Michael Niedermayer <michaelni@gmx.at>
Merge commit 'e67a87eac814c7805d18c983c43033a8a1bd62af'

* commit 'e67a87eac814c7805d18c983c43033a8a1bd62af':
  vf_(no)format: switch to an AVOptions-based system.
  af_aformat: switch to an AVOptions-based system.

Conflicts:
	doc/filters.texi
	libavfilter/af_aformat.c

Merged-by: Michael Niedermayer <michaelni@gmx.at>
Merge commit '62dcdb028cc84845fd263bb09304c4c6500bda7a'

* commit '62dcdb028cc84845fd263bb09304c4c6500bda7a':
  vf_blackframe: switch to an AVOptions-based system.
  vf_aspect: switch to an AVOptions-based system.

Conflicts:
	doc/filters.texi
	libavfilter/vf_aspect.c
	libavfilter/vf_blackframe.c

In the aspect filter most changes are merged but not the final
switch to the libav API because that is too restrictive and has
difficulty handling the syntax.

Merged-by: Michael Niedermayer <michaelni@gmx.at>
avfilter: support alternative keys in the alternative shorthand system

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avfilter/blackframe: add "thres" back as alternative

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