Add tap driver initialization and ifconfig for AIX.

Add tap driver initialization and ifconfig for AIX.

AIX is special... ifconfig only works if it can add the data to
the ODM right away, so setup a local enviromnment set that has
"ODMDIR=/etc/objrepos" in it (hard-coded, nobody changes that).

Only --dev tap or --dev tapNN are supported right now.  AIX has no
tun driver (so tun mode would need to dynamically add/remove ethernet
headers to/from AIX).

Signed-off-by: Gert Doering <gd@medat.de>
Acked-by: Arne Schwabe <arne@rfc2549.org>
Message-Id: <1402409073-54067216-3-git-send-email-gert@greenie.muc.de>
URL: http://article.gmane.org/gmane.network.openvpn.devel/8788
Signed-off-by: Gert Doering <gert@greenie.muc.de>