RFR: JDK-8257042: [aix] Disable os.release_one_mapping_multi_commits_vm gtest

[Thomas Stuefe]

On AIX, os::release_memory() cannot release multi-mappings since os::reserve_memory() may return system V shared memory instead of the usual mmapped memory. This makes a new gtest fail.

This is very difficult to fix, therefore lets just disable this test for now.

For details about the underlying issue, see https://bugs.openjdk.java.net/browse/JDK-8257041.

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patch disables the test for AIX, and also needs to disable the local reserve helper function to avoid an "unused symbol" warning.

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Commit messages:
 - disable multi map test on aix

Changes: https://git.openjdk.java.net/jdk/pull/1426/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1426&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8257042
  Stats: 4 lines in 1 file changed: 4 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1426.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1426/head:pull/1426

PR: https://git.openjdk.java.net/jdk/pull/1426