Document the new ".Fx" macro in the mdoc man pages. I also

changed the update(4) man page to use this new macro just to
have something to test it on.

share/man/man4/update.4

@@ -47,8 +47,9 @@ kernel process helps protect the integrity of disk volumes
 by flushing
 volatile cached filesystem data
 to disk at thirty second intervals.
-.Nm Update
-does the equivalent of the 
+The 
+.Nm update
+process does the equivalent of the 
 .Xr sync 2
 function call to do the task.
 .Sh SEE ALSO
@@ -69,5 +70,7 @@ An
 command appeared in
 .At v6 ,
 and was usually started by /etc/rc when the system went multi-user.
-.Nm Update
-was turned into a kernel initiated process in FreeBSD 2.0.
+A kernel initiated
+.Nm update
+process first appeared in
+.Fx 2.0 .

share/man/man7/mdoc.7

@@ -332,6 +332,7 @@ Produces
 .It Li \&Ef Ta \&No Ta \&No Ta "End font mode."
 .It Li \&Em Ta Yes Ta Yes Ta "Emphasis (traditional English)."
 .It Li \&Eo Ta Yes Ta Yes Ta "Enclose string open quote."
+.It Li \&Fx Ta \&No Ta \&No Ta Tn "FreeBSD operating system"
 .It Li \&No Ta Yes Ta Yes Ta "Normal text (no-op)."
 .It Li \&Ns Ta Yes Ta Yes Ta "No space."
 .It Li \&Pc Ta Yes Ta Yes Ta "Parenthesis close quote."

share/man/man7/mdoc.samples.7

@@ -550,6 +550,8 @@ The name of the operating system
 should be the common acronym, e.g.
 .Tn BSD
 or
+.Tn FreeBSD
+or
 .Tn ATT .
 The release should be the standard release
 nomenclature for the system specified, e.g. 4.3, 4.3+Tahoe, V.3,
@@ -559,6 +561,9 @@ For instance, a typical footer might be:
 .Pp
 .Dl \&.Os BSD 4.3
 .Pp
+or
+.Dl \&.Os FreeBSD 2.2
+.Pp
 or for a locally produced set
 .Pp
 .Dl \&.Os CS Department
@@ -567,9 +572,9 @@ The Berkeley default,
 .Ql \&.Os
 without an argument, has been defined as
 .Tn BSD
-Experimental in the
+in the
 site specific file
-.Pa /usr/src/share/tmac/doc-common .
+.Pa /usr/src/gnu/usr.bin/groff/tmac/doc-common .
 It really should default to
 .Tn LOCAL .
 Note, if the
@@ -1393,6 +1398,22 @@ callable. It accepts at most two arguments.
 The
 .Ql \&.Bx
 macro is parsed and is callable.
+.Ss FreeBSD Macro
+.Bd -literal -offset indent -compact
+Usage: .Fx Version.release ... \*(Pu
+.Ed
+.Bl -tag -width ".Fx 2.2 ) ," -compact -offset 14n
+.It Li ".Fx 2.2 ."
+.Fx 2.2 .
+.El
+.Pp
+The
+.Ql \&.Fx
+macro is
+.Em not
+parsed and
+.Em not
+callable. It accepts at most two arguments.
 .Ss UNIX Macro
 .Dl Usage: .Ux ... \*(Pu
 .Bl -tag -width ".Ux 4.3 ) ," -compact -offset 14n