Libva for wayland

[Zou, Nanhai]

Hi Kristensen,
	We are beginning to implement libva for Wayland.
	To display video frames on Wayland, we need to implement
	vaPutsurface for Wayland.

	There are 2 ways to determine if the surface associate with a window is a pixmap or an overlay.
	1. User set a flag to determine use a pixmap or overlay.
	2. Wayland to make the decision.

	Which option shall we choose?

	If we are going to use option 2, I think there should be an API for wayland to choose the surface from window id. Do you have suggestion for this API?

Thanks
Zou Nanhai