Deocument the meaning of a pid value of 0 and remove the BUGS section;

mostly from Jonathan Perkin in resolution of PR bin/15008.

bin/kill/kill.1

@@ -1,4 +1,4 @@
-.\"	$NetBSD: kill.1,v 1.13 2000/05/13 17:04:04 christos Exp $
+.\"	$NetBSD: kill.1,v 1.14 2001/12/20 15:13:08 kleink Exp $
 .\"
 .\" Copyright (c) 1980, 1990, 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -93,6 +93,9 @@ The following pids have special meanings:
 .It -1
 If superuser, broadcast the signal to all processes; otherwise broadcast
 to all processes belonging to the user.
+.It 0
+Broadcast the signal to all processes in the current process group
+belonging to the user.
 .El
 .Pp
 Some of the more commonly used signals:
@@ -140,9 +143,3 @@ A
 .Nm
 command appeared in
 .At v6 .
-.Sh BUGS
-A replacement for the command
-.Dq Li kill 0
-for
-.Xr csh  1
-users should be provided.