subcontrols. This will allow users to modify properties of the div -- for
example, adding a title element to the div. Access this property via
panel_div on the added control after addControls is called on the panel.
git-svn-id: http://svn.openlayers.org/trunk/openlayers@2973 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf