Take idle inhibitions into account for when to fire idle watches as
requested by OS components.
This should stop gnome-session and gnome-settings-daemon considering
the session idle when they have been inhibited for longer than their
timeout, for example to avoid the screensaver activating, or the
computer suspending after watching a film.
https://bugzilla.gnome.org/show_bug.cgi?id=705942
And use the old "native" backend for both X11 and Wayland. This will
allow us to share fixes between implementations without having to delve
into the XSync X11 extension code.
https://bugzilla.gnome.org/show_bug.cgi?id=705942
Right now this just has all of the files in one directory. We'll
be introducing more structure to this in the future, and build
a proper backend system.
