PR 197379: Add an option to run `syslogd' in the foreground

[rpokala-panasas.com]

Summary

Adds and documents an option to cause syslogd to run in the foreground. This allows a separate process to monitor when and how syslogd exits. That process can then restart syslogd if needed.

Test Plan

Run syslogd normally, and observe no changed behavior. Run syslogd with the new '-F' option, and observe that it runs in the foreground, but does not behave differently otherwise.

[allanjude]

the man page bits lgtm