Make GstVaapiVideoBuffer a simple wrapper for video meta. This buffer is
no longer necessary but for compatibility with GStreamer 0.10 APIs or users
expecting a GstSurfaceBuffer like Clutter.
The vdeo buffer creation routines shall actually be internal to gstreamer-vaapi
plugin elements. So deprecate any explicit creation routines that are not the
new *_typed_new*() variants.
Allow rendering flags, as a combination of GstVaapiSurfaceRenderFlags,
to be set to the video buffer. In particular, this is mostly useful for
basic deinterlacing.
Add helper function to bind a foreign buffer into a GstVaapiVideoBuffer.
Any image, surface or surface proxy will be inherited from the source buffer
if it is a GstVaapiVideoBuffer.