RFR: JDK-8322943: runtime/CompressedOops/CompressedClassPointers.java fails on AIX [v3]

[Joachim Kern]

> Even after recent fixes like
> https://bugs.openjdk.org/browse/JDK-8305765
> the test runtime/CompressedOops/CompressedClassPointers.java fails on AIX.
> 
> This error results from the fact, that on AIX the shmat() allocation granularity is 256MB instead of the standard Pagesize (4KB or 64KB).
> 
> Because my first proposal (PR 17708) of introducing a new method os::vm_shm_allocation_granularity() in the shared hotspot code was rejected I now encapsulate the difference in ifdef AIX brackets.

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

  copyright strings

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Changes:
  - all: https://git.openjdk.org/jdk/pull/18105/files
  - new: https://git.openjdk.org/jdk/pull/18105/files/4bed19d1..179b2474

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18105&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18105&range=01-02

  Stats: 2 lines in 2 files changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/18105.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18105/head:pull/18105

PR: https://git.openjdk.org/jdk/pull/18105