Now that both arguments to the _new_with_factory() constructors
are nullable, there's no good reason to keep a separate _new()
around. Just make gtk_list_view_new() and gtk_grid_view_new()
take both a model and a factory.
Change the apis in GtkListView, GtkColumnView and
GtkGridView to be explicitly about GtkSelectionModel,
to make it obvious that the widgets handle selection.
Update all users.
Make both gtk_list_view_new and gtk_list_view_new_with_factory
take a model as first argument, and make all arguments
allow-none and transfer full.
Update all callers.
Make gtk_tree_list_model_new() take the root model
as first argument, and make it transfer full, for
consistency with other wrapping list constructors.
Update all callers.
Still missing here: Make the model property writable,
and allow passing NULL in the constructor.
In 99.9% of all cases, these are just NULL, NULL.
So just do away with these arguments, people can
use the setters for the rare cases where they want
the scrolled window to use a different adjustment.
