RFR: 8140241: (fc) Data transfer from FileChannel to itself causes hang in case of overlap

[Brian Burkhalter]

This request proposes to fix a failure on macOS which occurs when transferring to or from a file channel from or to the same file channel when the source and destination intervals overlap.

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Commit messages:
 - 8140241: (fc) Data transfer from FileChannel to itself causes hang in case of overlap

Changes: https://git.openjdk.java.net/jdk/pull/5061/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5061&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8140241
  Stats: 163 lines in 6 files changed: 157 ins; 0 del; 6 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5061.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5061/head:pull/5061

PR: https://git.openjdk.java.net/jdk/pull/5061