The use of make-systemd-constructor appears to cause problems when connecting
via TLS (see: https://github.com/ngircd/ngircd/issues/330).
* gnu/services/messaging.scm (ngircd-global): [pid-file]: Set default value
and remove maybeness. Adjust doc.
* gnu/services/messaging.scm (ngircd-configuration): Adjust comment.
(ngircd-wrapper): Expose writable PID file and preserve pid namespace.
(ngircd-shepherd-service): Replace make-systemd-constructor with
make-forkexec-constructor and adjust surrounding accordingly.
(ngircd-activation): New procedure.
(ngircd-service-type): Extend activation-service-type with it.
Change-Id: Ic7c135ab45122e180107cde8bb9976426e3afbc4
e78f8a85bb