RFR: 5041655: (ch) FileLock: negative param and overflow issues

[Brian Burkhalter]

Add an implementation note to `java.nio.channels.FileLock.overlaps(long,long)` indicating that the method does not check its parameters. Adding such checks would be an incompatible change.

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Commit messages:
 - 5041655: (ch) FileLock: negative param and overflow issues

Changes: https://git.openjdk.java.net/jdk/pull/7254/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7254&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-5041655
  Stats: 7 lines in 1 file changed: 6 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7254.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7254/head:pull/7254

PR: https://git.openjdk.java.net/jdk/pull/7254