RFR [11] 8198358 : Align organization of DualStackPlainSocketImpl with TwoStacksPlainSocketImp [win]

[Ivan Gerasimov]

Hello!

I'd like to do the next step toward removing the TwoStacks socket 
implementation on Windows.

It would be aligning the two implementations (DualStack and TwoStacks), 
so they can be easier merged together during the next step.

There are three PlainSocketImpl implementations in JDK:
java.base/windows/classes/java/net/DualStackPlainSocketImpl.java
java.base/windows/classes/java/net/TwoStacksPlainSocketImpl.java
java.base/unix/classes/java/net/PlainSocketImpl.java

While two later have very similar organization (in particular, set of 
native methods), the former is organized slightly differently.
In order to merge the two Windows implementation together, they first 
need to be organized in a similar way.
For consistency, DualStack implementation will be reorganized to be 
aligned with TwoStacks and unix/PlainSocketImpl.

Bug: https://bugs.openjdk.java.net/browse/JDK-8198358
Webrev: http://cr.openjdk.java.net/~igerasim/8198358/00/webrev/

The change looks somewhat messy, but in fact it was a series of 
incremental changes, which I still keep in the mercurial 'mq'.

(I wish the webrev could be made incremental based on the mq patches, to 
make it easier to review.)

The patched JDK builds fine and all the regression tests pass Okay.


Thanks in advance!
-- 

With kind regards,
Ivan Gerasimov