RFR 9: 8132394 : (process) ProcessBuilder support for a pipeline of processes

[Roger Riggs]

Please review the new ProcessBuilder.startPipeline API, implementation, 
and tests.

The new method starts a Process for each ProcessBuilder, creating a 
pipeline of
processes linked by their standard output and standard input streams.
Each builder can use redirectErrorsream to coalesce error output with 
standard output.
But otherwise standard error streams are not modified.

The API is the same as discussed on the earlier core-libs thread [1] and 
addresses
the comments.

webrev:
    http://cr.openjdk.java.net/~rriggs/webrev-pipeline-8132394/

javadoc of ProcessBuilder:  only startPipeline is new:
    http://cr.openjdk.java.net/~rriggs/pipedoc/

Thanks, Roger

p.s. The PIPE_CHANNEL redirection proposed by Peter Levert is complementary
and still has a bug or two to work out.

[1] 
http://mail.openjdk.java.net/pipermail/core-libs-dev/2015-July/034634.html