RFR: 8198432: Remove Thread extension point

[Thomas Schatzl]

Hi,

On Mon, 2018-02-26 at 11:54 +0100, Stefan Johansson wrote:
> Hi,
> 
> Please review this small change to remove a now unused extension
> point.
> 
> Links
> JBS: https://bugs.openjdk.java.net/browse/JDK-8198432
> Webrev: http://cr.openjdk.java.net/~sjohanss/8198432/00/
> 
> Summary
> The Thread class extension support made it possible to add extra data
> to it. This is no longer needed since the internal code using it has
> been removed.
> 

  looks good.

Thomas