Gio::SimpleActionGroup: Some API improvements.
Gio::SimpleActionGroup: Some API improvements.

* gio/src/simpleactiongroup.hg: lookup(): Add a const version
  and use refreturn. Deprecate both lookup() methods,
  however, because they just call lookup_action() in the
  base ActionMap.
  Deprecate insert() and remove() because they just call
  add_action() and remove_action() in the base ActionMap,
  confusing the API.
  I filed bug #705600 about this API problem in the C API,
  hoping they can be deprecated there.

johne53/MB3Glibmm,GNOME/glibmm,GNOME/glibmm,GNOME/glibmm,GNOME/glibmm,johne53/MB3Glibmm,johne53/MB3Glibmm,GNOME/glibmm,johne53/MB3Glibmm