Screen locking protocol

[Pekka Paalanen]

Hi,

here is the screen locking protocol patch set for review. It does
not actually implement locking yet, only the protocol and hooks
intended for it.

To test, run the compositor with WAYLAND_DEBUG=1 to see the
protocol and -i 5 to have the idle timeout as 5 seconds.

Just before sending I noticed an odd problem. If I start and focus
a terminal, then let the screen go blank and locked, it will not
wake up. According to protocol dump, desktop-shell does send
'unlock' request, but the compositor never sees it. Any hints
to where the problem might be would be much appreciated.

Thanks,
pq