Fxi various man pages to stop abusing the .Bx macro to generate

the string "FreeBSD".  Use the .Fx macro instead.  Also did some
minor re-wording/formatting to work around a deficiency with
the .Fx macro when it comes to puncuation characters other than
periods and commas.

usr.bin/file/file.1

@@ -139,8 +139,8 @@ Cause symlinks to be followed, as the like-named option in
 .It Pa /usr/share/misc/magic
 default list of magic numbers (used to be
 .Pa /etc/magic
-in previous versions of
-.Bx Free )
+prior to
+.Fx 3.0 )
 .El
 .Sh ENVIRONMENT
 The environment variable

usr.bin/rpcgen/rpcgen.1

@@ -246,10 +246,10 @@ code for older versions
 of the operating system.
 .Pp
 Note: in
-.Bx Free ,
+.Fx ,
 this compatibility flag is turned on by
 default since
-.Bx Free
+.Fx
 supports only the older
 .Tn ONC RPC
 library.
@@ -291,7 +291,7 @@ This option is useful for optimization. The default size is 5.
 Note: in order to provide backwards compatibility with the older
 .Nm
 on the
-.Bx Free
+.Fx
 platform, the default is actually 0 (which means
 that inline code generation is disabled by default). You must specify
 a non-zero value explicitly to override this default.

usr.bin/truss/truss.1

@@ -64,6 +64,6 @@ The
 command was written by
 .An Sean Eric Fagan
 for
-.Bx Free Ns ;
-it was modeled after
+.Fx .
+It was modeled after
 similar commands available for System V Release 4 and SunOS.