RFR: 8292562: (fc) Use copy_file_range in FileChannel::transferTo on Linux [v4]

[Brian Burkhalter]

> Add `copy_file_range(2)` to the native Linux implementation of `FileChannel::transferTo`.

Brian Burkhalter has updated the pull request incrementally with one additional commit since the last revision:

  8292562: Add test of transferTo while target is appending

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Changes:
  - all: https://git.openjdk.org/jdk/pull/9925/files
  - new: https://git.openjdk.org/jdk/pull/9925/files/88750dc5..c3c36f1d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9925&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9925&range=02-03

  Stats: 105 lines in 1 file changed: 105 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/9925.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9925/head:pull/9925

PR: https://git.openjdk.org/jdk/pull/9925