wayland: require WAYLAND_DISPLAY be set to open wayland display
wayland: require WAYLAND_DISPLAY be set to open wayland display

The wayland client libraries now require WAYLAND_DISPLAY be set
to use them.

See:

http://cgit.freedesktop.org/wayland/wayland/commit/?id=fb7e13021730d0a5516ecbd3712ea4235e05d24d

This commit makes _gdk_wayland_display_open bail early if
WAYLAND_DISPLAY is unset, just as it does for XDG_RUNTIME_DIR.

jigpu/gtk,chergert/gtk,jadahl/gtk,grubersjoe/adwaita,alexlarsson/gtk,jadahl/gtk,alexlarsson/gtk,chergert/gtk,davidgumberg/gtk,davidgumberg/gtk,chergert/gtk,jigpu/gtk,grubersjoe/adwaita,jadahl/gtk,jadahl/gtk,grubersjoe/adwaita,jigpu/gtk,jadahl/gtk,alexlarsson/gtk,davidgumberg/gtk,chergert/gtk,jigpu/gtk,jadahl/gtk,chergert/gtk,grubersjoe/adwaita,chergert/gtk,davidgumberg/gtk,davidgumberg/gtk,jadahl/gtk,alexlarsson/gtk,grubersjoe/adwaita,grubersjoe/adwaita,grubersjoe/adwaita,alexlarsson/gtk,jigpu/gtk,chergert/gtk,jigpu/gtk,jadahl/gtk,davidgumberg/gtk,chergert/gtk,alexlarsson/gtk,alexlarsson/gtk,grubersjoe/adwaita,davidgumberg/gtk,alexlarsson/gtk,jigpu/gtk,jigpu/gtk,davidgumberg/gtk