RFR: 8274400: HotSpot Style Guide should permit use of alignof

[Julian Waters]

The alignof operator was added by C++11. It returns the alignment for the given type. Various metaprogramming usages exist, in particular when using std::aligned_storage. Use of this operator should be permitted in HotSpot code.

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Commit messages:
 - HotSpot Style Guide should permit use of alignof

Changes: https://git.openjdk.org/jdk/pull/11761/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11761&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8274400
  Stats: 5 lines in 2 files changed: 5 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/11761.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11761/head:pull/11761

PR: https://git.openjdk.org/jdk/pull/11761