pkgbase: Create a FreeBSD-syslogd package

This allow one to not install syslogd and use syslog-ng or any other
syslog daemon.
While here put some syslog.d file in their own package.

MFC after: 2 weeks
Sponsored by: Beckhoff Automation GmbH & Co. KG
Differential Revision: https://reviews.freebsd.org/D33455