Take maintainership of the port and add updated files.

The addition of the Kyuafile and tcptestsuite_atf_test script
make running the tests, once installed, simpler and easier
than in the past, e.g.

cd /usr/local/tests
sudo kyua -v test_suites.FreeBSD.allow_sysctl_side_effects=1 test

Submitted by: Olivier Cochard
Sponsored by: Rubicon Communications, LLC (d/b/a "Netgate")