Revert r555726: Support RFC5424/IETF syslog format.

There is a better way to support RFC5424/IETF syslog format implemented
in 12-STABLE, 13-STABLE, and 14-CURRENT.

PR: 252613
Reported by: Boris Korzun <drtr0jan@yandex.ru>
Reviewed by: Peter Czanik (CzP) <peter.czanik@oneidentity.com>

		Balabit (a OneIdentity company) / syslog-ng upstream