This adds support for the shortcut inhibitor protocol in gdk/wayland
backend.
A shortcut inhibitor request is issued from the gdk wayland backend for
both the older, deprecated API gdk_device_grab() and the new gdk seat
API gdk_seat_grab(), but only if the requested capability is for the
keyboard only.
https://bugzilla.gnome.org/show_bug.cgi?id=783343