Added a result_data argment to prop_copy()

lib/class.js

@@ -81,13 +81,19 @@ function Class() {};
  *
  * The destination object is directly modified.
  *
+ * The result data will be populated with information from the copy that may be
+ * useful to the creation of the class (e.g. list of the abstract methods).
+ *
  * @param  {Object}  props        properties to copy
  * @param  {Object}  dest         destination object
+ * @param  {Object}  result_data  object to store data regarding the copy in
  *
  * @return undefined
  */
-function prop_copy( props, dest )
+function prop_copy( props, dest, result_data )
 {
+    result_data = result_data || {};
+
     // copy each of the properties to the destination object
     for ( property in props )
     {