Update copyright to include 2018 plus company name change

Update copyright to include 2018 plus company name change

The autumn of 2017, OpenVPN Technologies, Inc changed name to just
OpenVPN Inc.  Otherwise, extend the copyright to cover 2018 as well.

With the exception of the company name change, all changes have been
performed by the dev-tools/update-copyright.sh script.

Signed-off-by: David Sommerseth <davids@openvpn.net>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20180131140314.11103-1-davids@openvpn.net>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg16418.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>
(cherry picked from commit 499794596deb16965164b611ff61c8609c6cd08e)