Log Message:
Update rsyslog to 8.7.0.

- add message metadata "system" to msg object
  this permits to store metadata alongside the message
- imfile: add support for "filename" metadata
  this is useful in cases where wildcards are used
- imptcp: make stats counter names consistent with what imudp, imtcp uses
- added new module "omkafka" to support writing to Apache Kafka
- omfwd: add new "udp.senddelay" parameter
- mmnormalize enhancements
- RainerScript "foreach" iterator and array reading support
- now requires liblognorm >= 1.0.2
- add support for systemd >= 209 library names
- BSD "ntp" facility (value 12) is now also supported in filter
- bugfix: global(localHostName="xxx") was not respected in all modules
- bugfix: emit correct error message on config-file-not-found
- bugfix: impstats emitted invalid JSON format (if JSON was selected)
- bugfix: (small) memory leak in omfile's outchannel code
- bugfix: imuxsock did not deactivate some code not supported by platform