Note the name change from mount_null to mount_nullfs in FreeBSD 5.0.

PR:		212541
Approved by:	bcr (mentor)
MFC after:	4 days
Differential Revision:	https://reviews.freebsd.org/D8105

sbin/mount_nullfs/mount_nullfs.8

@@ -33,7 +33,7 @@
 .\"     @(#)mount_null.8	8.6 (Berkeley) 5/1/95
 .\" $FreeBSD$
 .\"
-.Dd May 1, 1995
+.Dd October 3, 2016
 .Dt MOUNT_NULLFS 8
 .Os
 .Sh NAME
@@ -240,6 +240,10 @@ UCLA Technical Report CSD-910056,
 .Em "Stackable Layers: an Architecture for File System Development" .
 .Sh HISTORY
 The
-.Nm
+.Nm mount_null
 utility first appeared in
 .Bx 4.4 .
+It was renamed to
+.Nm
+in
+.Fx 5.0 .