Add warning for using connection block variables after connection blocks

In 2.3  some options that were allowed only in global config before have
been moved to connection blocks. This changes the behaviour if the
variables were defined after connection block. This patch adds a warning
to catch these mistakes.

Also let warnings errors show [CONNECTION-OPTIONS] instead of [CMD-LINE]
for connection blocks
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <1387275767-10303-1-git-send-email-arne@rfc2549.org>
URL: http://article.gmane.org/gmane.network.openvpn.devel/8117

Signed-off-by: Gert Doering <gert@greenie.muc.de>
(cherry picked from commit cd6555e0159987ef264789f4976053ce2aa5fc20)