We overrode the property for PowerSaveMode, which meant that gdbus's
auto-generated PropertiesChanged code wasn't being run.
This really confused gnome-rr and gnome-settings-daemon's power plugin
about the current DPMS state of the display, since they used their
cached PowerSaveMode properties, and never saw a PropertiesChanged being
emitted.
If a display was on, they set it to off, and then set it back on, the
setting back on would never fire, since they thought the display was
already off.
To fix this, remove our custom property override and just respond to
notifications on the object.
Namely, this fixes the DPMS management when receiving notifications so
that it now properly times out.
The output_id is more of an opaque identifier for the monitor, based on
its underlying ID from the windowing system. Since we also use the term
"output_id" for the output's index, rename our use of the opaque cookie
"output_id" to "winsys_id".
A gulong is not enough to get 64 bits in all arches, so we must
cast it, or we can corrupt the stack.
This was downstream bug bugzilla.redhat.com/show_bug.cgi?id=1002055
https://bugzilla.gnome.org/show_bug.cgi?id=707267
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.
