Fix configure interaction with static OpenSSL libraries

Add "-lcrypto" to configure OpenSSL "-lssl" test (if no pkg-config
found), otherwise linking with static OpenSSL libraries will fail.

Trac ticket #305

Message-Id: <521668C9.5070003@openvpn.net>
URL: http://article.gmane.org/gmane.network.openvpn.devel/7835
URL: https://community.openvpn.net/openvpn/ticket/305
Acked-By: Heiko Hund <heiko.hund@sophos.com>
Signed-off-by: Gert Doering <gert@greenie.muc.de>
(cherry picked from commit 30e358e5de352c8de04a955dc89f33e1710e9b97)