Copyright for hp2xx source package in Focal

Format: https://www.debian.org/doc/packaging-manuals/copyright-format/1.0/
Upstream-Name: hp2xx
Upstream-Contact: Martin Kroeker 
Source: https://www.gnu.org/software/hp2xx/

Files: *
Copyright: Copyright 1991 - 1994 (V3.20) Heinz W. Werntges
 Copyright 1999 - 2003 Martin Kroeker 
License: GPL-2
 hp2xx is distributed under the GNU GENERAL PUBLIC LICENSE.
 .
 On Debian GNU/Linux systems, the complete text of the GNU General Public
 License is found in `/usr/share/common-licenses/GPL-2'.

Files: debian/*
Copyright: Copyright 1999 - 2018 Christian T. Steigies 
License: GPL-2+
 On Debian GNU/Linux systems, the complete text of the GNU General Public
 License is found in `/usr/share/common-licenses/GPL-2'.