PolarSSL-1.2 support

PolarSSL-1.2 support

Add support for PolarSSL-1.2, which has changed the API in several places.
This is a minimal port, new features have not been enabled. Only PolarSSL
1.2.5 and newer are accepted, as earlier versions contain unresolved
(security) issues.

Signed-off-by: Joachim Schipper <joachim.schipper@fox-it.com>
Signed-off-by: Steffan Karger <steffan.karger@fox-it.com>
Acked-by: Adriaan de Jong <dejong@fox-it.com>
Message-Id: <1363942465-3251-2-git-send-email-steffan.karger@fox-it.com>
URL: http://article.gmane.org/gmane.network.openvpn.devel/7436
Signed-off-by: Gert Doering <gert@greenie.muc.de>
(cherry picked from commit 4a56d19fc3aa59d0eebd99f102ecaaa3665c5088)