[jdk8u-ri] RFR: 8201793: (ref) Reference object should not support cloning [v3]

[Poonam Bajaj]

> This changeset backports the fix for 8201793 to jdk8u-ri.
> 
> With this change, `java.lang.ref.Reference::clone` method always throws `CloneNotSupportedException`.

Poonam Bajaj has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains three commits:

 - fixed merge conflict
 - Fixed the javadoc comments
 - 8201793: (ref) Reference object should not support cloning

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Changes: https://git.openjdk.java.net/jdk8u-ri/pull/6/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk8u-ri&pr=6&range=02
  Stats: 121 lines in 2 files changed: 121 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk8u-ri/pull/6.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk8u-ri pull/6/head:pull/6

PR: https://git.openjdk.java.net/jdk8u-ri/pull/6