progress of data through a pipeline. It can be inserted into
any normal pipeline between two processes to give a visual
indication of how quickly data is passing through, how long
it has taken, how near to completion it is, and an estimate
of how long it will be until completion.
Author: Andrew Wood <andrew.wood@ivarch.com>
WWW: http://www.ivarch.com/programs/pv.shtml
PR: ports/66309
Submitted by: Daniel Roethlisberger <daniel@roe.ch>