Revert commit "Remove nav class also for ul element"

modules/mod_menu/tmpl/default.php

@@ -20,7 +20,7 @@
 
 // The menu class is deprecated. Use mod-menu instead
 ?>
-<ul<?php echo $id; ?> class="mod-menu<?php echo $class_sfx; ?>">
+<ul<?php echo $id; ?> class="mod-menu nav<?php echo $class_sfx; ?>">
 <?php foreach ($list as $i => &$item)
 {
 	$class = 'nav-item';