dns/knot-resolver: update 2.4.1 -> 3.1.0

PR: 230842
Submitted by: Leo Vandewoestijne <freebsd@dns.company> (maintainer)
Relnotes: https://www.knot-resolver.cz/2018-08-20-knot-resolver-3.0.0.html

		https://www.knot-resolver.cz/2018-11-02-knot-resolver-3.1.0.html