[jdk8u-dev] RFR: 8071507: (ref) Clear phantom reference as soft and weak references do [v2]

[Poonam Bajaj]

> Backport of 8071507 and 8143847 from jdk8u-ri to jdk8u-dev.
> 
>     8071507: (ref) Clear phantom reference as soft and weak references do
>     8143847: Remove REF_CLEANER reference category
> 
> With these changes, phantom references are automatically cleared by the garbage collector like soft and weak references.
> 
> The changes are clean backport apart from a little manual adjustment for the hunk at line 246 in referenceProcessor.cpp.

Poonam Bajaj has updated the pull request incrementally with one additional commit since the last revision:

  Updated copyright years

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Changes:
  - all: https://git.openjdk.org/jdk8u-dev/pull/94/files
  - new: https://git.openjdk.org/jdk8u-dev/pull/94/files/f0ee3e01..3a37a2f5

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk8u-dev&pr=94&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk8u-dev&pr=94&range=00-01

  Stats: 3 lines in 3 files changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk8u-dev/pull/94.diff
  Fetch: git fetch https://git.openjdk.org/jdk8u-dev pull/94/head:pull/94

PR: https://git.openjdk.org/jdk8u-dev/pull/94