Log Message:
gtkmm3: updated to 3.24.2

3.24.2 (stable):

Gdk:
* Window::create_similar_surface(): Fix a memory leak.
* Suppress warnings from deprecated GTimeVal in
    PixbufAnimation::get_iter()
    PixbufAnimationIter::advance()

Gtk:
* Fix memory leaks in
    IconTheme::list_icons()
    IconView::get_selected_icons()
    RecentManager::get_items()

Documentation:
* Gtk::Builder: Describe how to use it together with Glib::Property.

Demos:
* Fix the source code listing.