Import from NetBSD: `pgrep' and `pkill' utilities for finding and

Import from NetBSD: `pgrep' and `pkill' utilities for finding and
signalling processes by name.

This initial commit brings in the following files directly from
NetBSD, unchanged except for the addition of $DragonFly$ ID tags:

$NetBSD: Makefile,v 1.1 2002/03/01 11:21:58 ad Exp $
$NetBSD: pkill.1,v 1.8 2003/02/14 15:59:18 grant Exp $
$NetBSD: pkill.c,v 1.7 2004/02/15 17:03:30 soren Exp $

The next few commits will DragonFly-ize these files and hook them up
to the build.

Initially-requested-by: Munish Chopra <chopra at soulwax dot net>
Approved-by: dillon