Window: Add ::is-maximized property
Window: Add ::is-maximized property

	* Wrap ::is-maximzed property
	* Wrap gtk_window_is_maximized() accessor method

GNOME/gtkmm,johne53/MB3Gtkmm,GNOME/gtkmm,GNOME/gtkmm,johne53/MB3Gtkmm,johne53/MB3Gtkmm,GNOME/gtkmm