libidn is needed unconditionally for libgnunetdnsparser

git-svn-id: https://gnunet.org/svn/gnunet@32493 140774ce-b5e7-0310-ab8b-a85725594a96
USERNAME is a placeholder, not a variable

git-svn-id: https://gnunet.org/svn/gnunet@32494 140774ce-b5e7-0310-ab8b-a85725594a96