(NULL_PTR): Use the same definition as

	rtl.h and tree.h.

From-SVN: r1847

gcc/cexp.y

@@ -45,12 +45,22 @@ struct arglist {
   int argno;
 };
 
+/* Define a generic NULL if one hasn't already been defined.  */
+
 #ifndef NULL
 #define NULL 0
 #endif
 
+#ifndef GENERIC_PTR
+#if defined (USE_PROTOTYPES) ? USE_PROTOTYPES : defined (__STDC__)
+#define GENERIC_PTR void *
+#else
+#define GENERIC_PTR char *
+#endif
+#endif
+
 #ifndef NULL_PTR
-#define NULL_PTR (char *) NULL
+#define NULL_PTR ((GENERIC_PTR)0)
 #endif
 
 int yylex ();