cad/pcb-rnd: Update 3.1.6 => 3.1.7b, take maintainership

Maintainer wasn't active for the last 2 years.

News:

• http://www.repo.hu/projects/pcb-rnd/news.html

Release notes:

• http://www.repo.hu/projects/pcb-rnd/releases/relnotes-3.1.7.txt
• http://www.repo.hu/projects/pcb-rnd/releases/relnotes-3.1.7b.txt

Changelogs:

• http://www.repo.hu/projects/pcb-rnd/releases/changelog-3.1.7.txt
• http://www.repo.hu/projects/pcb-rnd/releases/changelog-3.1.7b.txt

• Make DOCS option really work
• Pet portclippy(1) and portfmt(1)

Approved by: yuri@ (Mentor)
Differential Revision: https://reviews.freebsd.org/D53249