Copyright for bison source package in Focal

Format: https://www.debian.org/doc/packaging-manuals/copyright-format/1.0/
Upstream-Name: Bison
Upstream-Contact: bug-bison@gnu.org
Source: https://ftp.gnu.org/pub/gnu/bison/
Files-Excluded: doc/figs doc/bison.info doc/bison.info.bak doc/bison.texi
Comment: GFDL documentation with Front-Cover Texts and Back-Cover Texts.

Files: *
Copyright: 1984, 1986, 1987-2015 Free Software Foundation, Inc.
License: GPL-3+
 On Debian systems, the full text of the GNU General Public License
 Version 3 can be found in the file
 '/usr/share/common-licenses/GPL-3'.

Files: debian/*
Copyright: 2015 Chuan-kai Lin 
License: GPL-2+
 On Debian systems, the full text of the GNU General Public License
 Version 2 can be found in the file
 '/usr/share/common-licenses/GPL-2'.