Rework diagnostics text

Remove unused #include

usr.bin/comm/comm.1

@@ -63,7 +63,7 @@ and lines in both files.
 The filename ``-'' means the standard input.
 .Pp
 The following options are available:
-.Bl -tag -width Ds
+.Bl -tag -width indent
 .It Fl 1
 Suppress printing of column 1.
 .It Fl 2
@@ -84,8 +84,9 @@ printed in column number three will have one.
 assumes that the files are lexically sorted; all characters
 participate in line comparisons.
 .Sh DIAGNOSTICS
-.Nm Comm
-exits 0 on success, >0 if an error occurred.
+The
+.Nm
+utility exits 0 on success, and >0 if an error occurs.
 .Sh SEE ALSO
 .Xr cmp 1 ,
 .Xr diff 1 ,

usr.bin/comm/comm.c

@@ -50,11 +50,9 @@ static const char rcsid[] =
 
 #include <ctype.h>
 #include <err.h>
-#include <errno.h>
 #include <limits.h>
 #include <locale.h>
 #include <stdio.h>
-#include <stdlib.h>
 #include <string.h>
 #include <unistd.h>