OpenSSL: SSLeay symbols are no longer available in OpenSSL 1.1

OpenSSL: SSLeay symbols are no longer available in OpenSSL 1.1

The old symbols do not exist anymore but the library gained new
equivalent symbols (OSSL). Use them instead of the old ones

Signed-off-by: Emmanuel Deloget <logout@free.fr>
Acked-by: Steffan Karger <steffan.karger@fox-it.com>
Message-Id: <9ce17efda7b1ed100e73554b1916c0bfa687d9d1.1487368114.git.logout@free.fr>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg14089.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>
(cherry picked from commit c828ffc648eebda20e2f9087248944fa0f52a582)