ui/gtk: Fix the license information

ui/gtk: Fix the license information

The license information in this file is very messy. A short note at
the beginning says GPL first, but the long boilerplate code then
talks about "GNU Lesser General Public License version 2.0". First,
there is no such version of the "GNU Lesser GPL", it only started with
version 2.1. In version 2.0, it was still called "GNU Library GPL"
instead. Second, you can easily get the license of this file wrong
if you only quickly glance at the long boilerplate code.

Anyway, looking at the text of the LGPL (see COPYING.LIB in the top
directory), the license clearly states in section "3." that one should
rather replace the license information with the GPL information in
such a case of a mixture instead. Thus let's clean up the confusing
statements and use the proper GPL text only.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-id: 1550731902-28842-1-git-send-email-thuth@redhat.com

[ kraxel: s/v2/v2+/ as requested by Daniel ]

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>