In vaapi 1.1.0 (which confusingly is libva release 2.1.0), they
introduced a new surface export API that is more efficient, and
we've been supporting that and the old API ever since (Feb 2018).
If we drop support for the old API, we can do some fairly nice cleanup
of the code.
Note that the pkgconfig entries are explicitly versioned by the API
version and not the library version. I confirmed the upstream pkgconfig
files.
Like hwdec_cuda, you get a big #ifdef mess if you try and keep the
OpenGL and Vulkan interops in the same file. So, I've refactored
them into separate files in a similar way.