Remove all the old 2.x and 3.x version annotations.
GTK+ 4 is a new start, and from the perspective of a
GTK+ 4 developer all these APIs have been around since
the beginning.
The wayland tablet protocol allows notifying the compositor with
descriptions of the actions performed by each tablet element. This
API call allows to hook up in to this wayland-specific feature.
https://bugzilla.gnome.org/show_bug.cgi?id=770026
GdkWaylandDeviceData conceptually gathers the data that belongs to
a seat, so it's been renamed (although the old typedef stays, plenty
of refactoring is due here...).
The methods in GdkSeatClass have also been implemented, the most
remarkable is ::grab, which ensures the grab is performed on all
the relevant "master" devices.
https://bugzilla.gnome.org/show_bug.cgi?id=759309
