gdk: Support GdkWayland
gdk: Support GdkWayland

We need to set up the Wayland display when using GDK and Wayland's
client-side API.

GNOME/clutter,jigpu/clutter,djdeath/clutter,djdeath/clutter,djdeath/clutter,GNOME/clutter,jigpu/clutter,djdeath/clutter,GNOME/clutter,Distrotech/clutter,GNOME/clutter,Distrotech/clutter,jigpu/clutter,Distrotech/clutter,GNOME/clutter,Distrotech/clutter,Distrotech/clutter,jigpu/clutter,Distrotech/clutter,jigpu/clutter,jigpu/clutter,djdeath/clutter,djdeath/clutter