This patch updates libva and it's drivers to a new 2.0.0 version, which bumps the shlib version, breaks ABI and also has an API change.
The patch also simplifies the ports a little and fixes the DEBUG option when present in the ports I manage.
The multimedia/mpv and multimedia/gstreamer1-vaapi ports needed fixing to compile due to the API changes. The patches I used are taken from thee upstream repositories:
If I forgot some dependent port please report that to me so I can bump PORTREVISION there too.