RFR: JDK-8318175 : AIX PPC64: Handle alignment of double in structs

[suchismith1993]

1. use pragma directive to handle alignment.

JBS Issue: [JDK-8318175](https://bugs.openjdk.org/browse/JDK-8318175)

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Commit messages:
 - Remove trailing whitespaces
 - Handling alignment for double in AIX.

Changes: https://git.openjdk.org/jdk/pull/16579/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16579&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8318175
  Stats: 14 lines in 2 files changed: 14 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/16579.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16579/head:pull/16579

PR: https://git.openjdk.org/jdk/pull/16579