(builtin_putnum): Minor fix

 /* GNU Mailutils -- a suite of utilities for electronic mail
-   Copyright (C) 1999, 2000, 2001, 2002, 2003 Free Software Foundation, Inc.
+   Copyright (C) 1999, 2000, 2001, 2002, 2003, 2005 Free Software Foundation, Inc.
 
    GNU Mailutils is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -1068,7 +1068,7 @@ static void
 builtin_putnum (struct mh_machine *mach)
 {
   char *p;
-  asprintf (&p, "%d", mach->arg_num);
+  asprintf (&p, "%ld", mach->arg_num);
   print_string (mach, 0, p);
   free (p);
 }