Make sure config.h or the copy of that gets included only once to reduce duplicate include

warnings.

lib/driver/_cdio_generic.c

@@ -1,5 +1,5 @@
 /*
-  Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009
+  Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2011
   Rocky Bernstein <rocky@gnu.org>
 
   This program is free software: you can redistribute it and/or modify
@@ -21,10 +21,9 @@
 
 #ifdef HAVE_CONFIG_H
 # include "config.h"
+# define __CDIO_CONFIG_H__ 1
 #endif
 
-static const char _rcsid[] = "$Id: _cdio_generic.c,v 1.27 2008/04/22 15:29:11 karl Exp $";
-
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>