added man page for /dev/sysmouse. (and activate it)

plus add appropriate xrefs now that we have {cd,sd,st}.9

share/man/man4/Makefile

@@ -4,7 +4,7 @@ MAN4=	bpf.4 ccd.4 cd.4 ch.4 ddb.4 divert.4 drum.4 fd.4 fpa.4 \
 	icmp.4 ifmib.4 inet.4 intro.4 ip.4 ipfirewall.4 \
 	lkm.4 lo.4 netintro.4 \
 	null.4 ppp.4 pt.4 pty.4 route.4 \
-	scsi.4 sd.4 sl.4 snp.4 st.4 su.4 tcp.4 \
+	scsi.4 sd.4 sl.4 snp.4 st.4 su.4 sysmouse.4 tcp.4 \
 	ttcp.4 termios.4 tty.4 udp.4 uk.4 update.4 unix.4 vn.4 worm.4 yp.4 \
 	zero.4
 

share/man/man4/cd.4

@@ -396,7 +396,8 @@ None.
 .Xr scsi 4 ,
 .Xr sd 4 ,
 .Xr disklabel 5 ,
-.Xr disklabel 8
+.Xr disklabel 8 ,
+.Xr cd 9
 .Sh BUGS
 The names of the structures used for the third argument to
 .Fn ioctl

share/man/man4/da.4

@@ -265,7 +265,8 @@ None.
 .Xr wd 4 ,
 .Xr disklabel 5 ,
 .Xr disklabel 8 ,
-.Xr fdisk 8
+.Xr fdisk 8 ,
+.Xr sd 9
 .Sh HISTORY
 The
 .Nm

share/man/man4/sa.4

@@ -388,7 +388,8 @@ Parameters set to this device become the default parameters for [en]rst0.3
 None.
 .Sh SEE ALSO
 .Xr mt 1 ,
-.Xr scsi 4
+.Xr scsi 4 ,
+.Xr st 9
 .Sh HISTORY
 This
 .Nm

share/man/man4/sd.4

@@ -265,7 +265,8 @@ None.
 .Xr wd 4 ,
 .Xr disklabel 5 ,
 .Xr disklabel 8 ,
-.Xr fdisk 8
+.Xr fdisk 8 ,
+.Xr sd 9
 .Sh HISTORY
 The
 .Nm

share/man/man4/st.4

@@ -388,7 +388,8 @@ Parameters set to this device become the default parameters for [en]rst0.3
 None.
 .Sh SEE ALSO
 .Xr mt 1 ,
-.Xr scsi 4
+.Xr scsi 4 ,
+.Xr st 9
 .Sh HISTORY
 This
 .Nm