Fix declaration of NULL.

Signed-off-by: Stefan Weil <weil@mail.berlios.de>

Index: trunk/dyngen-exec.h
===================================================================
--- trunk.orig/dyngen-exec.h	2009-02-06 22:15:33.000000000 +0100
+++ trunk/dyngen-exec.h	2009-02-06 22:16:03.000000000 +0100
@@ -91,7 +91,7 @@
 extern int fputs(const char *, FILE *);
 extern int printf(const char *, ...);
 #undef NULL
-#define NULL 0
+#define NULL ((void *)0)
 
 #if defined(__i386__)
 #define AREG0 "ebp"