RFR: 8274400: HotSpot Style Guide should permit use of alignof [v3]

[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.

Julian Waters has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains five additional commits since the last revision:

 - Make section more brief
 - Merge remote-tracking branch 'upstream/master' into alignof
 - More Descriptive Version
 - Merge remote-tracking branch 'upstream/master' into alignof
 - HotSpot Style Guide should permit use of alignof

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/11761/files
  - new: https://git.openjdk.org/jdk/pull/11761/files/5ec061a4..ac2c2c3f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11761&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11761&range=01-02

  Stats: 91 lines in 5 files changed: 35 ins; 23 del; 33 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