prenice (like pgrep and pkill) won't match itself. Also fix nearby typo.

Bump date. From Ted Unangst in PR 47880.

usr.bin/pkill/pkill.1

@@ -1,4 +1,4 @@
-.\"	$NetBSD: pkill.1,v 1.23 2010/12/07 09:00:23 enami Exp $
+.\"	$NetBSD: pkill.1,v 1.24 2013/06/03 20:44:01 dholland Exp $
 .\"
 .\" Copyright (c) 2002 The NetBSD Foundation, Inc.
 .\" All rights reserved.
@@ -27,7 +27,7 @@
 .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 .\" POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd December 7, 2010
+.Dd June 3, 2013
 .Dt PKILL 1
 .Os
 .Sh NAME
@@ -173,13 +173,14 @@ This option is valid only when given as the first argument to
 .Pp
 The
 .Fl l
-flag is also availale for
+flag is also available for
 .Nm prenice .
 .Pp
 Note that a running
-.Nm pgrep
+.Nm pgrep,
+.Nm pkill,
 or
-.Nm pkill
+.Nm prenice
 process will never consider itself or system processes (kernel threads) as
 a potential match.
 .Sh EXIT STATUS