Manpages of src:gem2deb in Debian stretch-backports

• dh-make-ruby(1)
• dh_ruby(1)
• dh_ruby_fixdepends(1)
• dh_ruby_fixdocs(1)
• gem2deb-test-runner(1)
• gem2deb(1)
• gem2tgz(1)
• gen-ruby-trans-pkgs(1)