Method swap

deps/concurrentqueue/concurrentqueue.h:653–662

	}
	
	void swap(ProducerToken& other) MOODYCAMEL_NOEXCEPT
	{
		std::swap(producer, other.producer);
		if (producer != nullptr) {
			producer->token = this;
		}
		if (other.producer != nullptr) {
			other.producer->token = &other;
		}
	}
	
	// A token is always valid unless:
	//     1) Memory allocation failed during construction