Add support for RFC5848, signed syslog messages

[troglobit]

NetBSD syslogd has support for signed syslog messages according to https://tools.ietf.org/html/rfc5848, this would be highly desirable for easily securing syslog without having the full blown TLS support.

The description sounds a lot like DNS Crypt or DNS Over TLS. What cryptography library were you thinking of using?

[troglobit]

The idea is still to track the upstream NetBSD and FreeBSD syslogd implementations. I have not looked into detail yet what they did, and what dependencies are introduced, but we will not re-implement the wheel.

Here's the NetBSD code, http://cvsweb.netbsd.org/bsdweb.cgi/src/usr.sbin/syslogd/