MDL-65779 mod_forum: Add privatereplies to the backup process

Author: Peter

mod/forum/backup/moodle2/backup_forum_stepslib.php

@@ -58,7 +58,7 @@ protected function define_structure() {
         $post = new backup_nested_element('post', array('id'), array(
             'parent', 'userid', 'created', 'modified',
             'mailed', 'subject', 'message', 'messageformat',
-            'messagetrust', 'attachment', 'totalscore', 'mailnow'));
+            'messagetrust', 'attachment', 'totalscore', 'mailnow', 'privatereplyto'));
 
         $tags = new backup_nested_element('poststags');
         $tag = new backup_nested_element('tag', array('id'), array('itemid', 'rawname'));