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

[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.

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Commit messages:
 - JDK-8329850

Changes: https://git.openjdk.org/jdk/pull/18676/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18676&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8329850
  Stats: 18 lines in 1 file changed: 13 ins; 0 del; 5 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