RFR: JDK-8301354: Modernize utilities/breakpoint.hpp [v3]

[Justin King]

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

Justin King has updated the pull request incrementally with one additional commit since the last revision:

  Fix reference to unqualified breakpoint
  
  Signed-off-by: Justin King <jcking at google.com>

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Changes:
  - all: https://git.openjdk.org/jdk/pull/12296/files
  - new: https://git.openjdk.org/jdk/pull/12296/files/af4bef60..1b016ec0

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12296&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12296&range=01-02

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 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