vdpau: Add support for AV1 decoding.
Add support for AV1 decoding.
My motivation here is realising that in Fedora 39, VLC no longer supports VA-API. Basically, FFMpeg is developing faster than VLC. And while the next major release of VLC will likely resolve the current problem, FFMpeg will likely have moved on by then too. IMO it is worth having VDPAU support available as a fall-back position for the more common codecs.