[ticket/11495] Explain whether move_children prepends/appends/overwrittes

PHPBB3-11495

phpBB/includes/nestedset/interface.php

@@ -85,6 +85,9 @@ interface phpbb_nestedset_interface
 	/**
 	* Moves all children of one item to another item
 	*
+	* If the new parent already has children, the new children are appended
+	* to the list.
+	*
 	* @param int	$current_parent_id	The current parent item
 	* @param int	$new_parent_id		The new parent item
 	* @return bool True if any items where moved