RFR (S) 8183198: Factor out thread state serialization into a proper helper function

[Mikael Gerdin]

Hi all,

Please review this small cleanup of the thread state serialization code.

Basically I suggest that we get rid of the platform specific 
interfaceSupport headers, put the Windows specific exception wrapper 
code in os_windows and let the other platforms share a os_posix variant.

I've also tried to name the helper functions to clarify what the 
difference between them is.

Testing: JPRT, local testing
Webrev: http://cr.openjdk.java.net/~mgerdin/8183198/webrev.0/
Bug: https://bugs.openjdk.java.net/browse/JDK-8183198

Thanks
/Mikael