[ticket/12966] Sort by post_time and post_id where applicable

This change was not applied to the search as this would require a larger
rewrite of the search methods.

PHPBB3-12966

phpBB/includes/mcp/mcp_main.php

@@ -1265,7 +1265,7 @@ function mcp_fork_topic($topic_ids)
 			$sql = 'SELECT *
 				FROM ' . POSTS_TABLE . "
 				WHERE topic_id = $topic_id
-				ORDER BY post_time ASC";
+				ORDER BY post_time ASC, post_id ASC";
 			$result = $db->sql_query($sql);
 
 			$post_rows = array();