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

warnings.

lib/driver/MSWindows/win32.c

@@ -1,5 +1,5 @@
 /*
-  Copyright (C) 2003, 2004, 2005, 2006, 2008, 2010 
+  Copyright (C) 2003, 2004, 2005, 2006, 2008, 2010, 2011
   Rocky Bernstein <rocky@gnu.org>
 
   This program is free software: you can redistribute it and/or modify
@@ -22,6 +22,7 @@
 
 #ifdef HAVE_CONFIG_H
 # include "config.h"
+# define __CDIO_CONFIG_H__ 1
 #endif
 
 static const char _rcsid[] = "$Id: win32.c,v 1.37 2008/04/21 18:30:21 karl Exp $";