Remove license.txt, it has been merged back in the main Dynare one

(cherry picked from commit 92feb083)

license.txt

-Format: https://www.debian.org/doc/packaging-manuals/copyright-format/1.0/
-Upstream-Name: Dynare-preprocessor
-Upstream-Contact: Dynare Team, whose members in 2020 are:
-                  - Stéphane Adjemian <stephane.adjemian@univ-lemans.fr>
-                  - Houtan Bastani <houtan@dynare.org>
-                  - Michel Juillard <michel.juillard@mjui.fr>
-                  - Frédéric Karamé <frederic.karame@univ-lemans.fr>
-                  - Dóra Kocsis <dora@dynare.org>
-                  - Junior Maih <junior.maih@gmail.com>
-                  - Ferhat Mihoubi <fmihoubi@univ-evry.fr>
-                  - Willi Mutschler <willi@mutschler.eu>
-                  - Johannes Pfeifer <jpfeifer@gmx.de>
-                  - Marco Ratto <marco.ratto@ec.europa.eu>
-                  - Sébastien Villemot <sebastien@dynare.org>
-                  Former Dynare Team members include:
-                  - Abdeljabar Benzougar
-                  - Alejandro Buesa
-                  - Fabrice Collard
-                  - Assia Ezzeroug
-                  - Stéphane Lhuissier
-                  - George Perendia
-Source: https://www.dynare.org
-
-Files: *
-Copyright: 1996-2020 Dynare Team
-License: GPL-3+
-
-Files: m4/ax_boost_base.m4
-       m4/ax_boost_system.m4
-       m4/ax_boost_filesystem.m4
-Copyright: 2008-2009 Thomas Porschberg <thomas@randspringer.de>
-           2009 Peter Adolphs
-           2008-2009 Michael Tindal
-           2008 Daniel Casimiro <dan.casimiro@gmail.com>
-           2009 Roman Rybalko <libtorrent@romanr.info>
-License: FSFAP
-
-Files: m4/ax_cxx_compile_stdcxx.m4
-       m4/ax_cxx_compile_stdcxx_17.m4
-Copyright: 2008 Benjamin Kosnik <bkoz@redhat.com>
-           2012 Zack Weinberg <zackw@panix.com>
-           2013 Roy Stogner <roystgnr@ices.utexas.edu>
-           2014, 2015 Google Inc.; contributed by Alexey Sokolov <sokolov@google.com>
-           2015 Paul Norman <penorman@mac.com>
-           2015 Moritz Klammler <moritz@klammler.eu>
-           2016, 2018 Krzesimir Nowak <qdlacz@gmail.com>
-           2019 Enji Cooper <yaneurabeya@gmail.com>
-License: FSFAP
-
-Files: m4/ax_latex_class.m4 m4/ax_tex_test.m4
-Copyright: 2008 Boretti Mathieu <boretti@eig.unige.ch>
-           2009 Dynare Team
-License: LGPL-2.1+
-
-License: GPL-3+
- Dynare 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.
- .
- Dynare is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- GNU General Public License for more details.
- .
- You should have received a copy of the GNU General Public License
- along with Dynare.  If not, see <http://www.gnu.org/licenses/>.
-
-License: GPL-3+ with Autoconf exception
- 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.
- .
- This program is distributed in the hope that it will be useful, but
- WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
- Public License for more details.
- .
- You should have received a copy of the GNU General Public License along
- with this program. If not, see <http://www.gnu.org/licenses/>.
- .
- As a special exception, the respective Autoconf Macro's copyright owner
- gives unlimited permission to copy, distribute and modify the configure
- scripts that are the output of Autoconf when processing the Macro. You
- need not follow the terms of the GNU General Public License when using
- or distributing such scripts, even though portions of the text of the
- Macro appear in them. The GNU General Public License (GPL) does govern
- all other use of the material that constitutes the Autoconf Macro.
- .
- This special exception to the GPL applies to versions of the Autoconf
- Macro released by the Autoconf Archive. When you make and distribute a
- modified version of the Autoconf Macro, you may extend this special
- exception to the GPL to apply to your modified version as well.
-
-License: LGPL-2.1+
- This library is free software; you can redistribute it and/or modify it
- under the terms of the GNU Lesser General Public License as published by
- the Free Software Foundation; either version 2.1 of the License, or (at
- your option) any later version.
- .
- This library is distributed in the hope that it will be useful, but
- WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
- General Public License for more details.
- .
- You should have received a copy of the GNU Lesser General Public License
- along with this library. If not, see <http://www.gnu.org/licenses/>.
-
-License: LGPL-3+
- This program is free software: you can redistribute it and/or modify
- it under the terms of the GNU Lesser General Public License as published by
- the Free Software Foundation, either version 3 of the License, or
- (at your option) any later version.
- .
- This program is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- GNU Lesser General Public License for more details.
- .
- You should have received a copy of the GNU Lesser General Public License
- along with this program.  If not, see <http://www.gnu.org/licenses/>.
-
-License: FSFAP
- Copying and distribution of this file, with or without modification, are
- permitted in any medium without royalty provided the copyright notice
- and this notice are preserved. This file is offered as-is, without any
- warranty.