RFR: JDK-8259372: remove AIX related USE_LIBRARY_BASED_TLS_ONLY and THREAD_LOCAL special handling [v2]

[Matthias Baesken]

> AIX 5.3 had buggy __thread support (see JDK-8176442).
> That's why we introduced a macro USE_LIBRARY_BASED_TLS_ONLY and set it only to 1 on AIX (different to the other platforms supported by the OpenJDK).
> However AIX 5.3 support was removed some time ago (currently we have a minimum requirement of AIX 7.X ) so the whole USE_LIBRARY_BASED_TLS_ONLY related coding could be removed.

Matthias Baesken has updated the pull request incrementally with one additional commit since the last revision:

  JDK-8259372: remove AIX related USE_LIBRARY_BASED_TLS_ONLY and THREAD_LOCAL special handling

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/1976/files
  - new: https://git.openjdk.java.net/jdk/pull/1976/files/aa98142c..3944582e

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=1976&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=1976&range=00-01

  Stats: 16 lines in 2 files changed: 16 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1976.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1976/head:pull/1976

PR: https://git.openjdk.java.net/jdk/pull/1976