Mention that bio(4) first appeared on NetBSD 4.0 too.

share/man/man4/bio.4

@@ -1,4 +1,4 @@
-.\"	$NetBSD: bio.4,v 1.4 2008/01/02 23:49:31 xtraeme Exp $
+.\"	$NetBSD: bio.4,v 1.5 2008/02/25 22:18:31 xtraeme Exp $
 .\"	$OpenBSD: bio.4,v 1.19 2006/09/20 22:22:37 jmc Exp $
 .\"
 .\" Copyright (c) 2002 Niklas Hallqvist
@@ -28,7 +28,7 @@
 .\" ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 .\" POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd January 2, 2008
+.Dd February 25, 2008
 .Dt BIO 4
 .Os
 .Sh NAME
@@ -128,7 +128,9 @@ ioctl tunnel device
 The
 .Nm
 driver first appeared in
-.Ox 3.2 .
+.Ox 3.2
+and
+.Nx 4.0 .
 .Sh AUTHORS
 .An -nosplit
 The