[Libva] Render to texture

[Zou, Nanhai]

Hi Jonathan,
	As we have discussed, people are interested to let libva be able to render to texture object.
	Form our driver level, it is pretty easy for our driver to render to a pixmap.
	However pixmap is X related concept. From the libva level, it is better to have an ID to represent some kind of texture object. How would you propose the "render to texture" API?

Thanks
Zou Nanhai