defect in comm help message

[Dan Bloch]

The "comm -help" ouput reads

                  -1              suppress lines unique to left file
                  -2              suppress lines unique to right file
                  -3              suppress lines unique to both files

The third line of this should say "suppress lines in both files" or
something like that.  Those line aren't unique.  As it stands, the usage
message is quite confusing (and comm usage is confusing enough!)

The Unix man page says, "Suppress the output column of lines duplicated  in
file1 and file2."

Cheers,
Dan