libavfilter: Add asettb filter for setting timebase for audio

Ported asettb (including the sr option for audio sample rate) from FFmpeg,
and copied/modified the existing settb documentation for asettb.

Signed-off-by: Katerina Barone-Adesi <katerinab+libav@gmail.com>
Signed-off-by: Anton Khirnov <anton@khirnov.net>
libx265: Use x265_param_parse to set the SAR

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
Merge remote-tracking branch 'qatar/master'

* qatar/master:
  libavfilter: Add asettb filter for setting timebase for audio

Conflicts:
	Changelog
	doc/filters.texi
	libavfilter/Makefile
	libavfilter/allfilters.c
	libavfilter/settb.c
	libavfilter/version.h

See: ba856c0be5599f21f241162e1f5f3f2506f3132c and others
Merged-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/x86: Exclude broken get_cabac under icl.

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