INT-3504: Deprecate `AmqpHeaders`

JIRA: https://jira.spring.io/browse/INT-3504

* Deprecate `AmqpHeaders` and extend it from `org.springframework.amqp.support.AmqpHeaders` for backward compatibility
* Change AMQP dependency to `1.4.0`
* Remove usage of deprecated `spring_reply_correlation` and `spring_reply_to` AMQP headers
* Fix syslog `DefaultMessageConverter` JavaDoc

Reformat code
INT-3507 TCP - Use BufferedOutputStreams

JIRA: https://jira.spring.io/browse/INT-3507

TcpNoDelay (false) helps to buffer IOs but only after the
first write.

Use `BufferedOutputStreams` for TCP writes.

Use the socket `sendBufferSize` for the buffer size.