Gtk2-Perl: Gtk3 0.007 available

Overview of changes in Gtk3 0.007 [2012-07-05]: Add overrides for Gtk3::ActionGroup; Add an override for Gtk3::show_about_dialog; Fix some test failures due to older dependencies. Gtk3 is available as a tarball: http://downloads.sourceforge.net/gtk2-perl/Gtk3-0.007.tar.gz or from git: