RFR: 8191441: (Process) add Readers and Writer access to java.lang.Process streams

[Roger Riggs]

Methods are added to java.lang.Process to read and write characters and lines from and to a spawned Process.
The Charset used to encode and decode characters to bytes can be specified or use the
operating system native encoding as is available from the "native.encoding" system property.

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Commit messages:
 - 8191441: (Process) add Readers and Writer access to java.lang.Process streams

Changes: https://git.openjdk.java.net/jdk/pull/4134/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4134&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8191441
  Stats: 416 lines in 2 files changed: 412 ins; 0 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4134.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4134/head:pull/4134

PR: https://git.openjdk.java.net/jdk/pull/4134