Implement sending response to challenge via CR_RESPONSE

Implement sending response to challenge via CR_RESPONSE

When a client announces its support to support text based
challenge/response via IV_SSO=crtext,the client needs to also
be able to reply to that response.

This adds the "cr-response" management function to be able to
do this. The answer should be base64 encoded.

Signed-off-by: Arne Schwabe <arne@rfc2549.org>
Acked-by: David Sommerseth <davids@openvpn.net>
Message-Id: <20200519220004.25136-4-arne@rfc2549.org>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg19907.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>