Adjust docblock of load_class()

refs c26b9ebb00e29be2e972fece3bcf73d33249a64b
diff --git a/system/core/Common.php b/system/core/Common.php
index 677ceaf..23b95a4 100644
--- a/system/core/Common.php
+++ b/system/core/Common.php
@@ -124,7 +124,7 @@
 	 *
 	 * @param	string	the class name being requested
 	 * @param	string	the directory where the class should be found
-	 * @param	string	the class name prefix
+	 * @param	string	an optional argument to pass to the class constructor
 	 * @return	object
 	 */
 	function &load_class($class, $directory = 'libraries', $param = NULL)