RFR: 8154238: Drop code to support Windows XP in windows socket impl

[Claes Redestad]

Hi,

more code in the Windows socket implementation that can be dropped

Bug: https://bugs.openjdk.java.net/browse/JDK-8154238
Webrev: http://cr.openjdk.java.net/~redestad/8154238/webrev.01/

Thanks!

/Claes