RFR: 8329850: [AIX] Allow loading of different members of same shared library archive [v5]

[Joachim Kern]

> With [JDK-8320890](https://bugs.openjdk.org/browse/JDK-8320890) we introduced the capability not to load shared libraries twice if the application wants to do that. Instead we just rise a ref counter. Unfortunately this also suppresses the loading of a second member of a shared library.
> This fix introduces an additionally stored hash value for each loaded member and only suppresses duplicate loading if the same member is loaded twice.
> If a shared library has no member a hash value of 0 is used to make the code orthogonal.

Joachim Kern has updated the pull request incrementally with one additional commit since the last revision:

  set ptr to nullptr after free

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Changes:
  - all: https://git.openjdk.org/jdk/pull/18676/files
  - new: https://git.openjdk.org/jdk/pull/18676/files/584502a8..97ad3670

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18676&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18676&range=03-04

  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/18676.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18676/head:pull/18676

PR: https://git.openjdk.org/jdk/pull/18676