Make syslog configurable again

Setting the logfile to 'syslog' did not work because it was treated as a
path and normalized to '/syslog', thwarting a later branch.  Allow it to
work again, and add a new 'syslog' configuration parameter which makes the
main program output to syslog, as well as any processes which do not have
a logfile explicitly set.
Skip formatting in syslog logging handler

As Syslog has its own way of dealing with log priority and timestamps, skip
the formatting stage and pass them through the way it is expecting.