RFR: 8272797: Mutex with rank safepoint_check_never imply allow_vm_block

[Coleen Phillimore]

See CR for details.  This essentially makes Mutex that safepoint_check_never imply a NoSafepointVerifier, which is a stronger and simpler invariant.
Tested with tier1-6.

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Commit messages:
 - 8272797: Mutex with rank safepoint_check_never imply allow_vm_block

Changes: https://git.openjdk.java.net/jdk/pull/5218/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5218&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8272797
  Stats: 28 lines in 9 files changed: 5 ins; 0 del; 23 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5218.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5218/head:pull/5218

PR: https://git.openjdk.java.net/jdk/pull/5218