RFR: 4619075: (ch) newChannel() should return Gathering/ScatteringByteChannel [v2]

[Brian Burkhalter]

> Modify `Channels.newChannel(InputStream)` and `Channels.newChannel(OutputStream)` to return `ScatteringByteChannel` and `GatheringByteChannel`, respectively.

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

  4619075: Change binary incompatible static covariant overrides to new methods

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5922/files
  - new: https://git.openjdk.java.net/jdk/pull/5922/files/fd41d0fb..0a4ff249

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5922&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5922&range=00-01

  Stats: 103 lines in 2 files changed: 74 ins; 13 del; 16 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5922.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5922/head:pull/5922

PR: https://git.openjdk.java.net/jdk/pull/5922