these layers are never base layers

git-svn-id: http://svn.openlayers.org/trunk/openlayers@628 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Layer/Markers.js

@@ -40,6 +40,13 @@ OpenLayers.Layer.Markers.prototype =
         }
     },
     
+    /** WFS layer is never a base class. 
+     * @type Boolean
+     */
+    isBaseLayer: function() {
+        return false;
+    },
+    
     /**
     * @param {OpenLayers.Marker} marker
     */

lib/OpenLayers/Layer/Text.js

@@ -40,6 +40,14 @@ OpenLayers.Layer.Text.prototype =
         OpenLayers.Layer.Markers.prototype.destroy.apply(this, arguments);
     },
     
+    /** WFS layer is never a base class. 
+     * @type Boolean
+     */
+    isBaseLayer: function() {
+        return false;
+    },
+    
+    
     /**
      * @param {?} ajaxRequest
      */

lib/OpenLayers/Layer/WFS.js

@@ -64,6 +64,13 @@ OpenLayers.Layer.WFS.prototype =
         OpenLayers.Layer.Markers.prototype.moveTo.apply(this, arguments);
     },
     
+    /** WFS layer is never a base class. 
+     * @type Boolean
+     */
+    isBaseLayer: function() {
+        return false;
+    },
+    
     /**
     * @param {String} name
     * @param {hash} params