RFR: 8278268 - (ch) InputStream returned by Channels.newInputStream should have fast path for FileChannel targets [v5]

[Markus KARG]

> This sub-issue defines the work to be done to implement JDK-8265891 solely for the particular case of FileChannel.transferFrom(ReadableByteChannel), including special treatment of SelectableByteChannel.

Markus KARG has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:

 - removed trailing whitespace
   
   Signed-off-by: Markus Karg <markus at headcrashing.eu>
 - testing 2GB+
   
   Signed-off-by: Markus Karg <markus at headcrashing.eu>
 - Implementing 8278268
   
   Signed-off-by: Markus Karg <markus at headcrashing.eu>

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/6711/files
  - new: https://git.openjdk.java.net/jdk/pull/6711/files/6aef12ae..3d658231

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=6711&range=04
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=6711&range=03-04

  Stats: 1078 lines in 76 files changed: 639 ins; 194 del; 245 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6711.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6711/head:pull/6711

PR: https://git.openjdk.java.net/jdk/pull/6711