* demos/gtk-demo/example_images.cc: Don't use Gtk::Picture::set_pixbuf().
* gdk/src/pixbuf.[ccg|hg]: Deprecate the create() method taking
a Cairo::Surface.
* gtk/gtkmm/selectionlistmodelimpl.h: Make Notebook a friend class.
* gtk/src/cssprovider.[ccg|hg]: Add commented lines that deprecate
load_from_data() and add load_from_string() and load_from_bytes().
* gtk/src/image.[ccg|hg]: Deprecate the set() method taking a Pixbuf.
* gtk/src/notebook.[ccg|hg]: get_pages() now returns an object that
implements both GListModel and GtkSelectionModel (like Stack::get_pages()).
Wrap it in a SelectionListModelImpl.
* gtk/src/picture.[ccg|hg]: Deprecate set_pixbuf().