[ticket/13713] Add mention BBCode

PHPBB3-13713

phpBB/phpbb/textformatter/data_access.php

@@ -138,6 +138,7 @@ class data_access
 			'email' => 10,
 			'flash' => 11,
 			'attachment' => 12,
+			'mention' => 13,
 		);
 
 		$styles = array();