syslogd has an altlog_proglist stanza, which can place the log socket
into a program's chroot directory, so it can still log.
This patch adds an equivalent to that for jails.
If used with jails, we lookup the each jail's "path" with jls appending
it to the sockfile and, now also privsockfile.
- syslogd must be restarted
- -H must be added to syslogd_flags before this is actually useful