hg: jdk/jdk: 8201793: (ref) Reference object should not support cloning

[mandy.chung at oracle.com]

Changeset: e3653598e3b0
Author:    mchung
Date:      2018-05-03 11:18 -0700
URL:       http://hg.openjdk.java.net/jdk/jdk/rev/e3653598e3b0

8201793: (ref) Reference object should not support cloning
Reviewed-by: psandoz, kbarrett

! src/java.base/share/classes/java/lang/ref/Reference.java
+ test/jdk/java/lang/ref/ReferenceClone.java