Downgrade master to the previous version

The latest release makes several ICON Buildbot tests at DWD fail (other builders seem to be fine though). We need a release of mtime that works with ICON and has the required license information. Therefore, we revert all changes in the Fortran and C source code to the state of d524da1d, which works.

.reuse/dep5

+Format: https://www.debian.org/doc/packaging-manuals/copyright-format/1.0/
+Upstream-Name: mtime
+Upstream-Contact: Luis Kornblueh <luis.kornblueh@mpimet.mpg.de>
+Source: https://gitlab.dkrz.de/icon-libraries/libmtime
+
+Files: Makefile.in
+Copyright: 1994-2021 Free Software Foundation, Inc.
+License: FSFULLRWD
+
+Files: */Makefile.in
+Copyright: 1994-2021 Free Software Foundation, Inc.
+License: FSFULLRWD
+
+Files: aclocal.m4
+Copyright: 1996-2021 Free Software Foundation, Inc.
+License: FSFULLR
+
+Files: config/compile
+Copyright: 1999-2021 Free Software Foundation, Inc.
+License: GPL-2.0-or-later WITH Autoconf-exception-generic
+
+Files: config/config.guess
+Copyright: 1992-2021 Free Software Foundation, Inc.
+License: GPL-3.0-or-later WITH Autoconf-exception-generic-3.0
+
+Files: config/config.h.in
+Copyright: 2013-2024 MPI-M, Luis Kornblueh, Rahul Sinha and DWD, Florian Prill. All rights reserved.
+License: CC0-1.0
+
+Files: config/config.sub
+Copyright: 1992-2021 Free Software Foundation, Inc.
+License: GPL-3.0-or-later WITH Autoconf-exception-generic-3.0
+
+Files: config/depcomp
+Copyright: 1999-2021 Free Software Foundation, Inc.
+License: GPL-2.0-or-later WITH Autoconf-exception-generic
+
+Files: config/install-sh
+Copyright: 1994 X Consortium
+License: X11-distribute-modifications-variant
+
+Files: config/ltmain.sh
+Copyright: 1996-2019, 2021-2022 Free Software Foundation, Inc.
+License: GPL-2.0-or-later WITH Libtool-exception
+
+Files: config/missing
+Copyright: 1996-2021 Free Software Foundation, Inc.
+License: GPL-2.0-or-later WITH Autoconf-exception-generic
+
+Files: config/py-compile
+Copyright: 2000-2021 Free Software Foundation, Inc.
+License: GPL-2.0-or-later WITH Autoconf-exception-generic
+
+Files: config/test-driver
+Copyright: 2011-2021 Free Software Foundation, Inc.
+License: GPL-2.0-or-later WITH Autoconf-exception-generic
+
+Files: configure
+Copyright: 1992-1996, 1998-2017, 2020-2021 Free Software Foundation, Inc.
+License: FSFUL
+
+Files: m4/libtool.m4
+Copyright: 1996-2001, 2003-2019, 2021-2022 Free Software Foundation, Inc.
+License: FSFULLR
+
+Files: m4/ltoptions.m4
+Copyright: 2004-2005, 2007-2009, 2011-2019, 2021-2022 Free Software Foundation, Inc.
+License: FSFULLR
+
+Files: m4/ltsugar.m4
+Copyright: 2004-2005, 2007-2008, 2011-2019, 2021-2022 Free Software Foundation, Inc.
+License: FSFULLR
+
+Files: m4/ltversion.m4
+Copyright: 2004, 2011-2019, 2021-2022 Free Software Foundation, Inc.
+License: FSFULLR
+
+Files: m4/lt~obsolete.m4
+Copyright: 2004-2005, 2007, 2009, 2011-2019, 2021-2022 Free Software Foundation, Inc.
+License: FSFULLR