RFR: JDK-8301354: Modernize utilities/breakpoint.hpp

[Justin King]

Cleanup `utilities/breakpoint.hpp` by utilizing compiler intrinsics when available, or normal signals for AIX/XLC.

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Commit messages:
 - Update missed AIX references
 - Modernize utilities/breakpoint.hpp

Changes: https://git.openjdk.org/jdk/pull/12296/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12296&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8301354
  Stats: 87 lines in 6 files changed: 38 ins; 42 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/12296.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12296/head:pull/12296

PR: https://git.openjdk.org/jdk/pull/12296