add removeLayer() function to Layers... implement it for EventPane so that it removes the extra 'pane' div when the layer is removed. (Closes #887)

git-svn-id: http://svn.openlayers.org/trunk/openlayers@4053 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Layer.js

@@ -418,6 +418,22 @@ OpenLayers.Layer = OpenLayers.Class({
         }
     },
     
+    /**
+     * APIMethod: removeMap
+     * Just as setMap() allows each layer the possibility to take a 
+     *     personalized action on being added to the map, removeMap() allows
+     *     each layer to take a personalized action on being removed from it. 
+     *     For now, this will be mostly unused, except for the EventPane layer,
+     *     which needs this hook so that it can remove the special invisible
+     *     pane. 
+     * 
+     * Parameters:
+     * map - {<OpenLayers.Map>}
+     */
+    removeMap: function(map) {
+        //to be overridden by subclasses
+    },
+    
     /**
      * APIMethod: getImageSize
      *