The skip-taskbar, skip-pager and urgency hints were
only ever implemented for X11, and are not very useful
with modern desktops. Relegate the functionality to
x11 backend api, and drop the GtkWindow api.
Rename all *window.[ch] source files.
This is an automatic operation, done by the following commands:
for i in $(git ls-files gdk | grep window); do
git mv $i $(echo $i | sed s/window/surface/);
git sed -f g $(basename $i) $(basename $i | sed s/window/surface/) ;
done
git checkout NEWS* po-properties po
