vaapi: libs: bump libva version requirement

Submitted by Víctor Manuel Jáquez Leal @vjaquez

Link to original bug (#797196)

Description

Nowadays the minimal requirement of VA-API version for gstremaer-vaapi is 0.30.4 (libva 1.0.0) which dates from 2009

Actually it is not currently tested that gstreamer-vaapi works with that ancient version.

ffmpeg requests 0.35.0 (libva 1.3.0) from 2014
mesa's state trackers requests 0.39.0 (libva 1.7.0) from 2016
libva-v4l2-request 0.34.0 (libva 1.2.0) from 2013

I would like to bump to 0.39, as mesa's state trackers, but also I would like to hear other opinions.