This adds support for xdg-output-unstable-v1 version 3, added in 1.
This new version deprecates zxdg_output_v1.done and replaces it with wl_output.done. If the version is high enough, there's no need to wait for both an xdg_output.done event and a wl_output.done event -- we only care about wl_output.done.
This MR has been tested with 2.
Signed-off-by: Simon Ser contact@emersion.fr