RFR (XS): 8198560: Remove implicit casts from oop to JavaThread* and jlong*

[Kim Barrett]

> On Feb 22, 2018, at 11:44 AM, Erik Österlund <erik.osterlund at oracle.com> wrote:
> 
> Hi,
> 
> In the current state, oop may be implicitly casted to JavaThread* and jlong*. There does not appear to be code relying on these casts, and therefore they should be removed. In the unlikely case this operation would make sense, then you may use cast_from_oop<JavaThread*>(obj) instead.
> 
> Webrev:
> http://cr.openjdk.java.net/~eosterlund/8198560/webrev.00/
> 
> Bug:
> https://bugs.openjdk.java.net/browse/JDK-8198560
> 
> Thanks,
> /Erik

Thank you Erik.  Looks good.

And I look forward to having C++11 explicit conversion operators.