func (v *Window) SetTitlebar(titlebar IWidget) {
	C.gtk_window_set_titlebar(v.native(), titlebar.toWidget())
}
func (v *Window) SetTitlebar(titlebar IWidget) {
	C.gtk_window_set_titlebar(v.native(), titlebar.toWidget())
}
/*
 * GtkWindow
 */
// SetTitlebar is a wrapper around gtk_window_set_titlebar().