net/freediameter: Fix build and unbreak port

Add new dependency dns/libidn for fix build [1]

While here, add LICENSE_FILE and bump PORTREVISION.

PR: 219145
Submitted by: Nikola Kolev <koue@chaosophia.net> (maintainer) [1]
Reported by: Vikash Badal <vikashb@where-ever.za.net>
Approved by: garga (mentor)
Differential Revision: https://reviews.freebsd.org/D10697