hg: jdk9/hs-rt/jdk: 8071507: (ref) Clear phantom reference as soft and weak references do

[kim.barrett at oracle.com]

Changeset: 42ccdfe56796
Author:    kbarrett
Date:      2015-12-28 14:03 -0500
URL:       http://hg.openjdk.java.net/jdk9/hs-rt/jdk/rev/42ccdfe56796

8071507: (ref) Clear phantom reference as soft and weak references do
Summary: GC clears phantom refs on notification; update spec accordingly.
Reviewed-by: mchung, jmasa

! src/java.base/share/classes/java/lang/ref/PhantomReference.java
! src/java.base/share/classes/java/lang/ref/package-info.java
+ test/java/lang/ref/PhantomReferentClearing.java