Shunt log messages to different endpoints depending on contents

Some messages -- like connection auditing ones -- are uninteresting to
users and they don't want to seem them.

Others, like system internal errors, are interesting (and rare enough)
to not be too voluminous for users but also deserve special treatment
at the audit endpoint.
Support optional protocol selection and simplistic syslog forwarding

This allows for wholesale forwarding of syslog, including headers,
which are boxed in another set of syslog-alike logplex headers.