RFR: 8334371: [AIX] Beginning with AIX 7.3 TL1 mmap() supports 64K memory pages [v5]

[Joachim Kern]

> Beginning with AIX 7.3 TL1 mmap() supports 64K memory pages. As an enhancement, during the initialization of the VM the availability of this new feature is examined. If the 64K pages are supported the VM will use mmap() with 64K pages instead of shmget()/shmat() with 64K pages due to the bad 256M alignment of shmget()/shmat().

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

  following Martins proposals

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Changes:
  - all: https://git.openjdk.org/jdk/pull/19771/files
  - new: https://git.openjdk.org/jdk/pull/19771/files/027843ef..ec42f924

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=19771&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=19771&range=03-04

  Stats: 23 lines in 4 files changed: 6 ins; 14 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/19771.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19771/head:pull/19771

PR: https://git.openjdk.org/jdk/pull/19771