XC is copyright (c) 2020 AI & IT UG (haftungsbeschränkt).  All rights
reserved.  Individual authors, whether or not specifically named,
retain copyright in all changes; in what follows, they are referred to
as XC Contributors. This is for convenience only and this body has no
legal status.  XC is distributed under the following licence; any
provisions made in individual files take precedence.

Permission is hereby granted, without written agreement and without
licence or royalty fees, to use, copy, modify, and distribute this
software and to distribute modified versions of this software for any
purpose, provided that the above copyright notice and the following
two paragraphs appear in all copies of this software.

In no event shall the XC Contributors be liable to any party for
direct, indirect, special, incidental, or consequential damages
arising out of the use of this software and its documentation, even if
the XC Contributors have been advised of the possibility of such
damage.

The XC Contributors specifically disclaim any warranties, including,
but not limited to, the implied warranties of merchantability and
fitness for a particular purpose.  The software provided hereunder is
on an "as is" basis, and the XC Contributors have no obligation to
provide maintenance, support, updates, enhancements, or modifications.