Makes save_timestamp conditional

- Add a .htconfig check to save_timestamp to prevent systematic
profiling
- Removes unused `mark_timestamp()` function including deleted code
comment

object/Conversation.php

@@ -145,7 +145,6 @@ class Conversation extends BaseObject {
 			$result[] = $item_data;
 		}
 
-		//$a->mark_timestamp();
 		return $result;
 	}