RFR: 8264146 Make Mutex point to rather than embed _name

[Coleen Phillimore]

This change removes the code that copies the name of a Mutex into a 64 char embedded array.
Tested with tier1 and performance tests on linux - startup/footprint , specjbb2015, dacapo and javac.

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Commit messages:
 - make Mutex name be const char*

Changes: https://git.openjdk.java.net/jdk/pull/3179/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3179&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8264146
  Stats: 14 lines in 2 files changed: 0 ins; 10 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3179.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3179/head:pull/3179

PR: https://git.openjdk.java.net/jdk/pull/3179