Copyright for os-prober source package in Trusty

The majority of code in os-prober is Copyright 2004-2011 by Joshua
Kwan, Joey Hess, Christian Perrier, Colin Watson and Otavio Salvador.
This is licensed $under the terms of the GNU GPL, either version 2 or,
at your option, any later version.


Some portions of os-prober by other contributors has an unclear license
of "GNU GPL", with the version not specified.

On Debian systems, a copy of the GNU General Public License is available in
/usr/share/common-licenses/GPL-2.