Use constrain_int() instead of MIN()+syshead.c compat definition - v2.

Reverts commit 15ca5c297b556fbb, instead change ssl_openssl.c to use
"constrain_int()", which already exists in "integer.h".

Using this instead of min_int() ensures that the result is always bounded
to 0...256 even in the case of a potential MAX_INT overflow.

Signed-off-by: Gert Doering <gert@greenie.muc.de>
Acked-by: David Sommerseth <davids@redhat.com>
Message-Id: 1367826941-22412-1-git-send-email-gert@greenie.muc.de
URL: http://article.gmane.org/gmane.network.openvpn.devel/7586
Signed-off-by: David Sommerseth <davids@redhat.com>