Makes wingpanel compile successfully against mutter 3.38 and a gala that was built against 3.38, but I was unable to test it at runtime because gala doesn't run on mutter 3.38 yet.
Should be safe to merge since it doesn't touch any code other than adding additional support for mutter 3.38 / libmutter-7.
Based on https://github.com/elementary/gala/pull/854
Makes wingpanel compile successfully against mutter 3.38 and a gala that was built against 3.38, but I was unable to test it at runtime because gala doesn't run on mutter 3.38 yet.
Should be safe to merge since it doesn't touch any code other than adding additional support for mutter 3.38 / libmutter-7.
Fixes: #339