vf_vapoursynth: add display resolution support

Add two new script environment variables 'video_in_dw' and
'video_in_dh', representing the display resolution of video. Along
with video resolution, sample ratio aspect can be calculated in
scripts.

Currently it's impossible to change sample ratio aspect with single
vapoursynth filter since '_SARNum' and '_SARDen' frame properties
from output clip will be ignored. A following 'dsize' filter is
necessary for this purpose.
vf_vapoursynth: add more VS frame properties

Add the missing frame properties in 48587e88.