+ /**
+ * <p>Extends one class to create a subclass and optionally overrides members with the passed literal. This method
+ * also adds the function "override()" to the subclass that can be used to override members of the class.</p>
+ * For example, to create a subclass of Ext GridPanel:
+ * <pre><code>
+MyGridPanel = Ext.extend(Ext.grid.GridPanel, {
+ constructor: function(config) {
+
+// Create configuration for this Grid.
+ var store = new Ext.data.Store({...});
+ var colModel = new Ext.grid.ColumnModel({...});
+
+// Create a new config object containing our computed properties
+// *plus* whatever was in the config parameter.
+ config = Ext.apply({
+ store: store,
+ colModel: colModel
+ }, config);
+
+ MyGridPanel.superclass.constructor.call(this, config);
+
+// Your postprocessing here
+ },
+
+ yourMethod: function() {
+ // etc.
+ }
+});
+</code></pre>
+ *
+ * <p>This function also supports a 3-argument call in which the subclass's constructor is
+ * passed as an argument. In this form, the parameters are as follows:</p>
+ * <div class="mdetail-params"><ul>
+ * <li><code>subclass</code> : Function <div class="sub-desc">The subclass constructor.</div></li>
+ * <li><code>superclass</code> : Function <div class="sub-desc">The constructor of class being extended</div></li>
+ * <li><code>overrides</code> : Object <div class="sub-desc">A literal with members which are copied into the subclass's
+ * prototype, and are therefore shared among all instances of the new class.</div></li>
+ * </ul></div>
+ *
+ * @param {Function} superclass The constructor of class being extended.
+ * @param {Object} overrides <p>A literal with members which are copied into the subclass's
+ * prototype, and are therefore shared between all instances of the new class.</p>
+ * <p>This may contain a special member named <tt><b>constructor</b></tt>. This is used
+ * to define the constructor of the new class, and is returned. If this property is
+ * <i>not</i> specified, a constructor is generated and returned which just calls the
+ * superclass's constructor passing on its parameters.</p>
+ * <p><b>It is essential that you call the superclass constructor in any provided constructor. See example code.</b></p>
+ * @return {Function} The subclass constructor from the <code>overrides</code> parameter, or a generated one if not provided.
+ */