RFR: 8191441: (Process) add Readers and Writer access to java.lang.Process streams [v6]

[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.

Roger Riggs has updated the pull request incrementally with one additional commit since the last revision:

  Corrected change from IllegalArgumentException to IllegalStateException and tests.

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4134/files
  - new: https://git.openjdk.java.net/jdk/pull/4134/files/37bfa009..bf5fc724

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4134&range=05
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4134&range=04-05

  Stats: 8 lines in 2 files changed: 0 ins; 0 del; 8 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