RFR: 8275840: Testing FileChannel.transferTo(FileChannel) with more than 2 GB of data

[Markus KARG]

Testing `FileChannel.transferTo(FileChannel)` with more than 2 GB of data is covering the case that *multiple* iterations of `FileChannel.transferTo(FileChannel)` are actually performed by the test.

This change was requested Alan Bateman @AlanBateman.

-------------

Commit messages:
 - Testing FileChannel.transferTo(FileChannel) with more than 2 GB of data

Changes: https://git.openjdk.java.net/jdk/pull/6093/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6093&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8275840
  Stats: 28 lines in 1 file changed: 28 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6093.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6093/head:pull/6093

PR: https://git.openjdk.java.net/jdk/pull/6093