* src/system.h (EXIT_SUCCESS, EXIT_FAILURE): Ensure a proper

definition.
* src/main.c (main): Use them.
Suggested by Hans Aberg.

src/main.c

@@ -119,7 +119,7 @@ main (int argc, char *argv[])
 
   output_files ();
 
-  exit (complain_message_count ? 1 : 0);
+  return complain_message_count ? EXIT_FAILURE : EXIT_SUCCESS;
 }
 
 /* Abort for an internal error denoted by string S.  */