MonitorManager: add a KMS backend

Using the new Cogl API to actually modeset (because we can't
use the DRM API directly without controlling buffer swap), we
can finally have a KMS monitor backend, which means full display
configuration when running on bare metal.

https://bugzilla.gnome.org/show_bug.cgi?id=706308
[NOT FOR REVIEW] Add the ability to attach a debugger at init
Set DISPLAY and WAYLAND_DISPLAY for dbus activated services and for autostarted apps

Call the appropriate method on gnome-session so that autostarted
and bus activated apps see the X server and wayland socket.

https://bugzilla.gnome.org/show_bug.cgi?id=706421
Stop messing with process groups

We can be launched by gnome-session now, which implies gdb must be
attached from outside, and the Ctrl-C problem is gone.

https://bugzilla.gnome.org/show_bug.cgi?id=706421
wayland: don't require Clutter backend variables to be set from outside

When running under mutter-launch, we can assume we're running on
bare metal, and set the clutter backend appropriately.

https://bugzilla.gnome.org/show_bug.cgi?id=706421
wayland: die when gnome-session asks us to

At logout, we want to die when gnome-session tells us. Previously,
we were relying on the X server going down (killed by GDM at the
end of the session), but we can't use that in wayland.

https://bugzilla.gnome.org/show_bug.cgi?id=706421
wayland: implement resizing and maximization for wayland clients

To properly resize clients, we need to send them configure events
with the size we computed from the constraint system.
Also, once the sizing is properly wired up, we need to make
sure that the size at the initial map is correct, and not
always 0, 0 (because the buffer is not yet converted into
a CoglTexture by MetaShapedTexture), otherwise we end up sending
out configure events at 1 x 1. To do so, we cache the surface
type in the initial state until the first commit.

Note that this does not handle interactive resizing yet, it
merely makes the API calls work for wayland clients.

While we're there, let's implement transient hints too.
(I may have to separate this out...)

https://bugzilla.gnome.org/show_bug.cgi?id=707401
wayland: implement global and window keybindings

Synthetize XInput events from ClutterEvents in MetaWaylandKeyboard,
and pass them to the keybindings infrastructure for early handling,
so that we can activate them even if the currently focused window
is not an X11 one (or if there is no focused window, or we're
modal)

https://bugzilla.gnome.org/show_bug.cgi?id=706963
wayland: sync the keymap from X to wayland

When X clients change the keyboard map, the also update a property
on the root window. We can notice that and rebuild our data structures
with the new values, as well as inform the wayland clients.

This is a terrible hack, and it's not how we want to implement things
in 3.12, but it's enough to have the same keyboard layout in the
shell, in X clients and in wayland clients in 3.10, until we decide
on the fate of the keyboard g-s-d plugin.

https://bugzilla.gnome.org/show_bug.cgi?id=707446
wayland: use the timestamps from events

Clutter has learned to use monotonic times for the events, and
so does X (at least Xwayland, which is an implementation we know
and we can rely upon), so the values are directly comparable.

https://bugzilla.gnome.org/show_bug.cgi?id=707466
display: shortcut get_time_roundtrip() when running as a wayland compositor

In wayland, we can make some assumptions about the behavior and
configuration of the X server (which is Xwayland), including on
the time it uses, and that way avoiding a roundtrip (potentially deadly, if
by chance the X server is also blocking on us or needs us to flush
the wayland socket buffer).
Note that we bypass get_current_time() entirely, as it is assumed
the function is called always to translated CurrentTime into a real
value.

https://bugzilla.gnome.org/show_bug.cgi?id=707466
wayland: implement HW cursors

Use the DRM API and libgbm to upload cursor buffers to the
appropriate HW plane, saving on GL calls and compositing.

https://bugzilla.gnome.org/show_bug.cgi?id=707573
MetaCursorTracker: add support for loading cursors from the theme

Not only this way we get the right Adwaita cursor as the default
(instead of shipping our own in png format), but we also add
support for all MetaCursors as root cursor (which most important
should allow us to have I-beams in shell entries)

https://bugzilla.gnome.org/show_bug.cgi?id=707573
wayland: add support for pointer barriers

Use the clutter pointer constrain callback and a lot of copypasted
code from Xorg to implement reactive pointer barriers and pointer
barrier events.

https://bugzilla.gnome.org/show_bug.cgi?id=706655
wayland: implement support for popup surfaces

Popup surfaces are mapped into override_redirect surfaces
of a DROPDOWN_MENU type, with the addition of a special pointer
grab.

https://bugzilla.gnome.org/show_bug.cgi?id=707863