RFR: 8269853: Prefetch::read should accept pointer to const

[Harold Seigel]

Please review this fix for JDK-8269853 to add 'const' to the first argument to Prefetch::read().  The fix was tested by running Mach5 tiers 1-2 on Linux, Mac OS, and Windows, and doing Mach5 builds for linux-s390, linux-x86, linux-zero, and linux-ppc.

Thanks, Harold

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Commit messages:
 - 8269853: Prefetch::read should accept pointer to const

Changes: https://git.openjdk.java.net/jdk/pull/6114/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6114&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8269853
  Stats: 24 lines in 13 files changed: 0 ins; 0 del; 24 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6114.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6114/head:pull/6114

PR: https://git.openjdk.java.net/jdk/pull/6114