RFR: 8274400: HotSpot Style Guide should permit use of alignof [v4]

[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 seven additional commits since the last revision:

 - <type_traits>
 - Merge remote-tracking branch 'upstream/master' into alignof
 - 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/ac2c2c3f..cc5c61a4

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11761&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11761&range=02-03

  Stats: 50 lines in 6 files changed: 18 ins; 26 del; 6 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