Copyright for mixer.app source package in Xenial

This package was debianized by Andreas Metzler 

Debian maintainer history:
   Marcelo E. Magallon 
   Adam Klein 

It was downloaded from http://www.fukt.bth.se/~per/mixer/

Upstream Author by Per Liden 

The original licence is as follows. A copy of the GPL can be found on
/usr/share/common-licenses/GPL on a debian system.

//  Mixer.app
//
//  Copyright (c) 1998-2002 Per Liden
//
//  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 2 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, write to the Free Software
//  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
//  USA.