evas/image: Add video surface caps.

evas/image: Add video surface caps.

Wayland subsurfaces can be used as video surfaces too, similarly to
Ecore_X windows. However, they support a different set of features. Some
of them, like subsurface clipping and scaling, might be added in the
future, but so far we must work with what we have.

This commit allows to set an enum bitfield to the Video_Surface, with
the default value being one that will keep the same behavior as before,
for Ecore_X window. Thus, backward compatibility should not be broken.

It's possible to inform Evas that the surface in question is not able to
resize or scale, or that it's above or below the original canvas
surface. This allows Evas to show the surface itself, or use a buffer of
pixels instead, when the capabilities are not available.