libvpx: do not mark VP9 as experimental when using libvpx >= 1.3.0

Signed-off-by: Diego Biurrun <diego@biurrun.de>
Merge remote-tracking branch 'qatar/master'

* qatar/master:
  libvpx: do not mark VP9 as experimental when using libvpx >= 1.3.0

Conflicts:
	libavcodec/libvpxdec.c
	libavcodec/libvpxenc.c

Merged-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/mpeg4video: fix 2 more incorrectly associated comments

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avfilter/vf_mergeplanes: specify pixel format min/max

Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>