[jdk8u-ri] RFR: 8201793: (ref) Reference object should not support cloning [v2]

[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 incrementally with one additional commit since the last revision:

  Fixed the javadoc comments

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Changes:
  - all: https://git.openjdk.java.net/jdk8u-ri/pull/6/files
  - new: https://git.openjdk.java.net/jdk8u-ri/pull/6/files/365622e1..a0966941

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk8u-ri&pr=6&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk8u-ri&pr=6&range=00-01

  Stats: 3 lines in 1 file changed: 2 ins; 0 del; 1 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