It is generally a good idea to license individual files under the
same terms as the project license (in particular when the mismatch
boils down to having copied the wrong license header), so relicense
the code under the LGPL.
https://bugzilla.gnome.org/show_bug.cgi?id=781422
Pick up the setting from the org.gnome.desktop.wm.preferences schema
if available. It is slightly more involved than other settings, as
the actual button names used in the schema differ from the ones we
use, so we need an additional translation step.
https://bugzilla.gnome.org/show_bug.cgi?id=731273