RFR: 8143847: Remove REF_CLEANER reference category

[Mandy Chung]

> On Jan 8, 2016, at 11:46 AM, Kim Barrett <kim.barrett at oracle.com> wrote:
> 
> Please review this change to remove the REF_CLEANER reference
> category.  Now that JDK-8071507 has changed PhantomReferences
> (REF_PHANTOM) to also be cleared when notified, the distinction
> between REF_CLEANER and REF_PHANTOM is no longer needed.
> 
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8143847
> 
> Webrev:
> http://cr.openjdk.java.net/~kbarrett/8143847/webrev.00/

Looks good.  It’s good to see this REF_CLEANER be removed.

Mandy