Add additional info to mkdir(1), mkfifo(1) and chmod(1)-manpages

chmod.1

@@ -54,6 +54,8 @@ read | write | execute | setuid and setgid | sticky
 .It Fl R
 Change modes recursively
 .El
+.Sh SEE ALSO
+.Xr umask 1
 .Sh STANDARDS
 The
 .Nm

mkdir.1

@@ -18,7 +18,8 @@ if it does not already exist.
 .It Fl m
 Set the file
 .Ar mode
-of newly created directories.
+of newly created directories. See
+.Xr chmod 1 .
 .It Fl p
 Also create necessary parent directories and
 do not fail if

mkfifo.1

@@ -17,7 +17,8 @@ if it does not already exist.
 .It Fl m
 Set the file
 .Ar mode
-of newly created named pipes.
+of newly created named pipes. See
+.Xr chmod 1 .
 .El
 .Sh SEE ALSO
 .Xr mkfifo 3