RFR: 8259067: bootclasspath append takes out object lock

[Coleen Phillimore]

See CR for details.
I made the classpath append list lock-free.  Calling experts in Atomic operations...
Tested with tier1-6.
Thanks,
Coleen

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Commit messages:
 - 8259067: bootclasspath append takes out object lock

Changes: https://git.openjdk.java.net/jdk/pull/1935/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1935&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8259067
  Stats: 48 lines in 4 files changed: 20 ins; 7 del; 21 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1935.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1935/head:pull/1935

PR: https://git.openjdk.java.net/jdk/pull/1935