constructors which take an object of the same class as its first argument are
mis-detected as method call with "self" argument by the GIR scanner. Using the
new (constructor) annotation from bug 561264, mark some of them as proper
constuctors, so that you can call them with NULL as first argument from
bindings; in particular, this fixes gdk_window_new() and the
gtk_radio_button_new_with*() constructors.