Update the GPL2 text to the latest revision

This patch replaces the GPL2 text with the latest one from:

 https://www.gnu.org/licenses/old-licenses/gpl-2.0.txt



The FSF moved to a different location quite a while ago already, and
the latest revision recommends to use the LGPL-2.1 ("Lesser" license)
instead of the LGPL-2.0 ("Library" license) in certain cases.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20190520072720.14755-1-thuth@redhat.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>