anymore, preferring OpenLayers.Function.bind(function, object), we don't
need to provide this -- so if someone provides something different, don't
clobber it. (Closes#962)
git-svn-id: http://svn.openlayers.org/trunk/openlayers@4339 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf