2.4.5:

* Gtk::Settings::get_default(): Correct reference-count error.
  (Murray Cumming)
* Gtk::ActionGroup, EntryCompletion, UIManager: Make constructors 
  protected instead of private (Christopher Palm).
* Examples: TreeView:
  - Added popup example, from gtkmm 2.2.
  - drag_and_drop: Correct vfuncs.
* Documentation:
  - libglademm memory management.
  - Tell people to check pkg-config for 2.4, not 2.2. 
  - Gtk::TreeSortable: Document sort function return value. 
  (Murray Cumming)