RFR: 7903448: JMH: Override the use of compiler hints using a system property [v2]

[Gilles Duboscq]

> Using `-Djmh.compilerhints.mode=true` will force the use of compiler hints. `-Djmh.compilerhints.mode=false` will prevent the use of compiler hints. When the system property is not set, the current beahviour based on vm name and version will be used by default.
> 
> This is especially useful when working with uncommon / rare JVMs or when adding compiler hints support to a new JVM.
> 
> I considered auto-detecting support for compiler hints but that didn't fit very well in the current code and required much more intrusive changes.

Gilles Duboscq has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:

  Allow forcing the use of compiler hints using a system property
  
  Using `-Djmh.compilerhints.mode=FORCE_ON` will force the use of compiler
  hints. `-Djmh.compilerhints.mode=FORCE_OFF` will prevent the use of compiler
  hints. When the system property is not set, or when it is set to `AUTO`,
  the current beahviour based on vm name and version will be used.

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Changes:
  - all: https://git.openjdk.org/jmh/pull/96/files
  - new: https://git.openjdk.org/jmh/pull/96/files/8996a68e..5e550e44

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jmh&pr=96&range=01
 - incr: https://webrevs.openjdk.org/?repo=jmh&pr=96&range=00-01

  Stats: 49 lines in 2 files changed: 39 ins; 0 del; 10 mod
  Patch: https://git.openjdk.org/jmh/pull/96.diff
  Fetch: git fetch https://git.openjdk.org/jmh.git pull/96/head:pull/96

PR: https://git.openjdk.org/jmh/pull/96