Log Message:
Update to 2.2.1.  Changes in this version:

* configure depends on ATK 1.2. (Murray Cumming)
* Various gtkmm/gdkmm reference-counting corrections, using
  refreturn. (Sven Grottke, Murray Cumming)
* Gtk::Menu_Helpers::Element: lifetime refcounting fix.
  (Murray Cumming)
* Glib:
  - build_path(), build_filename(): fix and performance
    improvement.
  - replace deprecated __builtin_bzero().
  (Daniel Elstner)
* Win32:
  2.2 now builds, after lots of work. And there's
  an installer. (Cedric Gustin)
* Documentation:
  - Glib::Cond documented (Rick L Vinyard Jr)
  - Review and completion of Gtk::AccelGroup -> Gtk::Bin
    (Bryan Forbes)
  - Minor internals docs fix. (Martin Schulze)