This removes the hardcoded value for the field (16) and the equivalent
hardcoded lengths in logmsg(..).
This change is being done to help stage future work to add RFC5424/RFC5434
support to syslogd(8).
Obtained from: Isilon OneFS (dcd33d13da) (as part of a larger change)
Submitted by: John Bauman <john.bauman@isilon.com>
MFC after: 2 weeks
Sponsored by: Dell EMC Isilon
15f0eea574