Support logging to syslog

Simply set the logfile path to "syslog" and murmur will log to syslog.

This should be stable, it has approximately 4 user-months of testing.
> openlog (const char *ident, int option, int facility)

Is there no constant for option `0`? What does `0` mean? No adjustment I guess?

Why not use `LOG_KERN` as the facility parameter though? That’s what you effectively do, right?
Shouldn’t it be `LOG_USER /* random user-level messages */` though?