RFR: 8305341: Alignment outside of HotSpot should be enforced by alignas instead of compiler specific attributes

[Julian Waters]

C11 has been stable for a long time on all platforms, so native code can use the standard alignas operator for alignment requirements

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Commit messages:
 - <stdalign.h>
 - GSSLibStub.c
 - ArrayReferenceImpl.c
 - Alignment outside of HotSpot should be enforced by alignas instead of compiler specific attributes

Changes: https://git.openjdk.org/jdk/pull/13258/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13258&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8305341
  Stats: 12 lines in 3 files changed: 3 ins; 0 del; 9 mod
  Patch: https://git.openjdk.org/jdk/pull/13258.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13258/head:pull/13258

PR: https://git.openjdk.org/jdk/pull/13258