syslogd: allow network and local messages to use different formats

[wollman]

Summary

I need to be able to submit logs to a log server in RFC5424 format, but I don't want to change the format of local log files. I added a -r option that controls only the format of network destinations. I've given up my commit bit, so if this is accepted I'll be trying to recruit a src committer to push this.

Test Plan

We're running this in production now, sending to a graylog server, and once my colleagues who manage that service fix it so I can access it again, I'll be making sure that the messages are getting received an parsed properly.

[bcr]

OK from manpages.