ProcessBuilder support for pipelines

[Roger Riggs]

On most operating systems, creating pipelines of processes is simple and 
direct.
That same function is missing from the Java Process support and can be 
provided by
java.lang.ProcessBuilder by enabling the pipes created for stdout to be
used for standard input when the processes are created.
Comments and feedback are appreciated on the prototype API and 
implementation.

Javadoc:  java.lang.ProcessBuilder.startPipe:
http://cr.openjdk.java.net/~rriggs/pipedoc/java/lang/ProcessBuilder.html#startPipe-java.lang.ProcessBuilder...-

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

Thanks, Roger