RFR: 8291895: Remove PRAGMA_NONNULL_IGNORED from x86 and AArch64

[Andrew Haley]

I fixed the underlying bugs, so the warnings are now superfluous. Build on GCC 11.0.3 and GCC head.

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Commit messages:
 - Merge https://github.com/openjdk/jdk into JDK-8291895
 - Remove PRAGMA_NONNULL_IGNORED from x86 and AArch64

Changes: https://git.openjdk.org/jdk/pull/9742/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9742&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8291895
  Stats: 34 lines in 7 files changed: 0 ins; 33 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/9742.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9742/head:pull/9742

PR: https://git.openjdk.org/jdk/pull/9742