Add client-only support for peer-id.

This is a reduced version of the peer-id patch from Lev Stipakov
implementing only the client side bits - send IV_PROTO=2, accept
"peer-id <n>" as pushed option, support P_DATA_V2 packets.

v2: remove addition of "struct tls_multi;" to options.h, not needed

Signed-off-by: Gert Doering <gert@greenie.muc.de>
Acked-by: Steffan Karger <steffan.karger@fox-it.com>
Message-Id: <1416770250-92680-1-git-send-email-gert@greenie.muc.de>
URL: http://article.gmane.org/gmane.network.openvpn.devel/9274