pgm: Attempt to detect a broken pipe and exit silently

pgm: Attempt to detect a broken pipe and exit silently

When piping output to another program, the other pipe may exit
before we are done. An example is "jgit log|head". The result is
that errno get set to EPIPE. Unfortunately Java does not have
specific exception for this so we have to look at the exception
message and hope that the number of variants are small.

The detection here seem to work on Windows, Linux and OS X and it
seems the message is usually not localized.

Change-Id: Id6968ea7a53ae27ba5496303f1a479e41e41fdcc