[syslog-ng] hashing and verify

[Fabien Wernli]

Hi Domenico,

I may have misread your message, but it seems to me you're comparing the
md5sum of the standard template i.e. `${ISODATE} ${HOST} ${MSGHDR}${MSG}`
from your command line with the md5sum of `${MESSAGE}`, which obviously
don't match.

# command line

> $ echo "Mar 15 08:23:15 void systemd[1]: Started System Logger Daemon." |
> md5sum -

# rewrite rule

>     set("$(md5 $MESSAGE)", value("MYMESS"));