We need to tell clutter's evdev backend about the desktop's key repeat
settings so that our own key bindings event processing and
gnome-shell's chrome widgets get their fake key events for continuous
key press as they expect.
Note that the wayland frontend filters out these events and thus
wayland clients do not see them as specced.
https://bugzilla.gnome.org/show_bug.cgi?id=728055
We'll need this in the wayland frontend to send a modifiers event to
clients.
Note that on X11 this isn't needed because key events include the
group index encoded in modifier state. If we ever want to make the
wayland frontend work with the X11 backend we'll handle it then.
https://bugzilla.gnome.org/show_bug.cgi?id=736433
These methods allow us to set and get xkbcommon keymaps as well as
locking a specific layout in a layout group.
With this, we introduce dependencies on xkeyboard-config, xkbfile,
xkbcommon-x11 and a libX11 new enough to have xcb support.
https://bugzilla.gnome.org/show_bug.cgi?id=734301
