Document the fact that comm(1) does not recognize multibyte characters

in its input. Although doing so would require only trivial changes,
it would be incompatible with the ordering used by sort(1), which is the
primary source of comm's input.

usr.bin/comm/comm.1

@@ -35,7 +35,7 @@
 .\"     From: @(#)comm.1	8.1 (Berkeley) 6/6/93
 .\" $FreeBSD$
 .\"
-.Dd June 6, 1993
+.Dd June 25, 2004
 .Os
 .Dt COMM 1
 .Sh NAME
@@ -101,3 +101,9 @@ A
 .Nm
 command appeared in
 .At v4 .
+.Sh BUGS
+The
+.Nm
+utility does not recognize multibyte characters in order to remain
+compatible with the current implementation of
+.Xr sort 1 .