lavfi: rename AVFilterBufferRefVideoProps.pixel_aspect to sample_aspect_ratio
Improve consistency with libavcodec.
This breaks libavfilter API/ABI.
The non-sequential 2.1.0 -> 2.4.0 bump is due to the mess previouslydone with the lavfi minor number.
lavfi: put color source in a dedicated file
Move the color source code from vf_pad.c to vsrc_color.c.
Signed-off-by: Michael Niedermayer <firstname.lastname@example.org>