Fix argument type warning introduced by http extra proxy header patch.

d0cb816cf8be68359617b61a55799f6330901f6a introduced add_proxy_headers(),
passing "port" as "const char *" - but it should be an "int".  As port
is not yet actually used inside add_proxy_headers(), it's just a warning.

Signed-off-by: Gert Doering <gert@greenie.muc.de>
Acked-by: Arne Schwabe <arne@rfc2549.org>
Message-Id: <1384526517-6020-1-git-send-email-gert@greenie.muc.de>
URL: http://article.gmane.org/gmane.network.openvpn.devel/7973