Make output keep track of surfaces.
Do not ever execute context sensitive stuff betwee mid page-flip.
(This may need bit less fragile design)
Rename output surface to bsurface to avoid name conflict with wayland
surfaces.
Make it possible to requery outputs from backend.
We destroy output surface on activity == false event, and re-assign it
after acitivty == true. We can also do hotpluggin the same way.
However backend holds now too much logic for this
(wlc_compositor_get_surfaless_output)
Add asserts, remove comment.
Mods should be exact ctrl + alt, nothing else for tty switch.