[libvirt] RFC: advertising graphics support (vnc, spice, sdl)

Currently consumers of libvirt's APIs must assume/attempt to define a VM that uses spice, vnc, or sdl without knowing if the actual hypervisor supports it. Obviously my discussion is very QEMU oriented but it would be good to leave expansion for the future. I was thinking that under the <guest> element for the capabilities we can add something like: <graphics> <spice/> <vnc/> <sdl/> </graphics> It would be at the same level as <arch> and <features>. But before I implemented this I wanted a sanity check if people think this is the best place or the best naming convention. Thanks. -- Doug Goldstein