irc/unreal: Update to 6.1.8.1

• Port now installs unrealircdctl helper and the unrealircd helper script
• Adjustments to port Makefile layout

Co-authored with port maintainer (previous iteration) and additional
improvements by committer

Changelog: https://forums.unrealircd.org/viewtopic.php?t=9390

PR: 275987
Reviewed by: tanawts@gmail.com (maintainer)
Tested by: tanawts@gmail.com (maintainer)