(バージョン情報なし。おそらく SVN 版にしか存在しないでしょう)
AMQPQueue::ack — Acknowledge the receipt of a message
This method allows the acknowledgement of a message that is retrieved with the AMQP_NOACK flag through AMQPQueue::get or AMQPQueue::consume
The message delivery tag of which to acknowledge receipt.
The only valid flag that can be passed is AMQP_MULTIPLE.