mountd: Update exports.5 for commit 7c5146da12

Commit 7c5146da12 modified mountd so that it uses
strunvis(3) to decode directory names in exports lines.
This allows special characters, such as blanks, to be
encoded in the directory names.

This patch updates the exports.5 man page for this change.

This is a content change.

(cherry picked from commit 922e78f65f)

usr.sbin/mountd/exports.5

@@ -27,7 +27,7 @@
 .\"
 .\"     @(#)exports.5	8.3 (Berkeley) 3/29/95
 .\"
-.Dd August 16, 2022
+.Dd December 21, 2023
 .Dt EXPORTS 5
 .Os
 .Sh NAME
@@ -108,6 +108,17 @@ any
 or
 .Dq Pa ..
 components.
+Pathnames are decoded by
+.Xr strunvis 3
+allowing special characters to be included in the directory name(s).
+In particular, whitespace, such as embedded blanks in directory names
+can be handled.
+For example, a blank can be encoded as \(rs040.
+.Xr vis 1
+with the
+.Fl M
+option may be used to encode directory name(s) with embedded special
+characters.
 Mount points for a file system may appear on multiple lines each with
 different sets of hosts and export options.
 .Pp
@@ -584,6 +595,8 @@ NFSv4 mount request for a directory that the client does not have
 permission for will succeed and read/write access will fail
 afterwards, whereas NFSv3 rejects the mount request.
 .Sh SEE ALSO
+.Xr vis 1 ,
+.Xr strunvis 3 ,
 .Xr nfsv4 4 ,
 .Xr netgroup 5 ,
 .Xr mountd 8 ,