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.
This patch changes all uses of GDK_DEPRECATED(_FOR) in gtk headers
by the versioned variants, GDK_DEPRECATED_IN_3_x(_FOR). At the same
time, we add GDK_AVAILABLE_IN_3_x annotations for all API additions
in 3.2 and 3.4.
This is a special-purpose button that can be used together with
GPermission objects to control the sensitivity of system settings.
Suitable permission objects can e.g. be obtained from PolicyKit.
http://bugzilla.gnome.org/show_bug.cgi?id=626457
