It includes:
* Expose a proper focusable state, instead of the default one from
cally, using StWidget::can_focus, and also notifying the state change
* Management of the selected stated, using the current pseudo_class.
* Defines a new virtual method on StWidget: get_accessible_type. In
this way it is not required to reimplement get_accessible just for
a accessible type change. get_accessible is reimplemented using this.
You can see that as a substitute of the atk object factory
https://bugzilla.gnome.org/show_bug.cgi?id=636716
