RFR: 8191441: (Process) add Readers and Writer access to java.lang.Process streams [v4]

[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:

  Described charset mapping of malformed chars in outputWriter
  Repeated calls to  inputReader, errorReader, and outputWriter now return the same instance
  and check for inconsistent charset argument
  Added warnings about concurrently use of input/output streams and readers/writers.

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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/7724b82c..a5ed7b73

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4134&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4134&range=02-03

  Stats: 161 lines in 2 files changed: 131 ins; 0 del; 30 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