Don't expose GstVaapiContext APIs and make them totally private to
libgstvaapi core library. That API would also tend to disappear in
a future revision. Likewise, don't expose GstVaapiDisplayCache API
but keep symbols visible so that the various render backends could
share a common display cache implementation in libgstvaapi.
Try to clean-up the documentation from any stale entry too.
Implement the new render-to-pixmap API. The only supported pixmap format
that will work is xRGB, with native byte ordering. Others might work but
they were not tested.
Add API to transfer VA urfaces to native pixmaps. Also add an API to
render a native pixmap, for completeness. In general, rendering to
pixmap would only be useful to certain VA drivers and use cases on
X11 display servers. e.g. GLX_EXT_texture_from_pixmap (TFP) handled
in an upper layer.
Drop GstVaapiImageFormat helpers since everything was moved to the new
GstVideoFormat based API. Don't bother with backwards compatibility and
just bump the library major version afterwards.
