RFR [11] 8058965 : Remove IPv6 support from TwoStacksPlainSocketImpl [win]

[Chris Hegarty]

Hi Ivan,

> ...
> Bug: https://bugs.openjdk.java.net/browse/JDK-8058965
> Webrev: http://cr.openjdk.java.net/~igerasim/8058965/00/webrev/

Thanks for taking this on. Of course you could go further ( remove
some overrides that are now identical to the superclass ), but a
steady incremental approach is good ( for reviewers too ).

Looks good.

-Chris.