Convert syslog listener to be a child process

Now syslog messages processing is part of the main event loop. Maybe it'd be better to make it a separate child attached to the same controlling terminal. The only drawback is that every message from pinito should be sent to syslog instead then.

Begin by locating the syslog message-processing code and the main event loop in the repository. Trace how the listener is attached to the controlling terminal and how pinito messages currently reach syslog; the work is done when the proposed child-process arrangement and message forwarding behavior are defined and covered by appropriate checks.

Written by the indexing model from the issue text.