I was looking for a utility to forward traffic from a legacy
application which is not IP6 aware to a newer one which is; doing some
research, socat seemed to fit my needs, so I installed it.  However,
it did not understand TCP6 options of IPv6 format addresses, and
"socat -V" revealed that it had been built with "#undef WITH_IP6".
Not sure why this was, I downloaded the source and tried to use
cygport to build it myself, but the configuration test for IPv6
support failed, so it still disabled it.

I had thought that cygwin 1.7 had IPv6 support, but
http://blog.gentilkiwi.com/programmes/socat#englishversion seems to
imply that it's not "native".  (I understand that that page seems to
be for a non-official release, and there's no date on it, so I can't
be sure which version of Cygwin it's even referring to, but it seems
to be the only place that actually makes a statement on the issue...)
Is there an inherent limitation in IPv6 support under Cygwin that will
keep socat from working, or did I just miss my opportunity in the
cygport build step that can actually get it to work?

I'm running Windows 7, and IPv6 support seems to be enabled on my
computer; ipconfig does show my computer as having an IPv6 address,
for instance, and I can use the Windows telnet tool to connect to my
IPv6 server at that address.

Cygcheck attached.