toString implementation for Filter.

If Format.CQL is not included in the build, toString from Object will be used.

lib/OpenLayers/Filter.js

@@ -56,7 +56,7 @@ OpenLayers.Filter = OpenLayers.Class({
     
     /**
      * APIMethod: clone
-     * Clones this filter. Should be implementted by subclasses.
+     * Clones this filter. Should be implemented by subclasses.
      * 
      * Returns:
      * {<OpenLayers.Filter>} Clone of this filter.
@@ -65,5 +65,23 @@ OpenLayers.Filter = OpenLayers.Class({
         return null;
     },
     
+    /**
+     * APIMethod: toString
+     *
+     * Returns:
+     * {String} Include <OpenLayers.Format.CQL> in your build to get a CQL
+     *     representation of the filter returned. Otherwise "[Object object]"
+     *     will be returned.
+     */
+    toString: function() {
+        var string;
+        if (OpenLayers.Format && OpenLayers.Format.CQL) {
+            string = OpenLayers.Format.CQL.prototype.write(this);
+        } else {
+            string = Object.prototype.toString.call(this);
+        }
+        return string;
+    },
+    
     CLASS_NAME: "OpenLayers.Filter"
 });