Copyright for gnat source package in Bionic

Format: https://www.debian.org/doc/packaging-manuals/copyright-format/1.0/

Files: *
Copyright: 2009-2014 Ludovic Brenta 
           2014-2017 Nicolas Boulenguez 
License: GPL-3+
 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation, either version 3 of the License, or
 (at your option) any later version.
 .
 On Debian GNU/Linux systems, the full terms of the GNU General Public
 License are in /usr/share/common-licenses/GPL-3.