Based on the original implementation (hybrid-screenclone) by
Tomáš Janoušek, and Bumblebee integration by Kevin Puetz.

intel-virtual-output utilizes local VirtualHeads to present a contiguous
desktop to the local display manager, but maps the drawing on those
outputs to the remote display, and provides bidirectional RandR proxy so
that you can resize the remote display and configure it within your
desktop. The remote display should also send hotplug events back to the
local desktop, for reconfiguration on the fly.

Ideally the remote display is a discrete GPU on the same host so that we
can use local Shared Memory transport and avoid sending data over the
wire (though it will work in that setup). Ideally you would have userptr
support to provide zero-copy rendering between the GPUs, or have dma-buf
(in which case you would be using PRIME). For remote rendering, no
compression is done so this fares worse than VNC.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>