fix some header files to conform with C99 hopefully, should fix issue #1670

include/string.h

@@ -36,11 +36,17 @@
 #ifndef _STRING_H
 #define _STRING_H
 
+/* NULL pointer */
+#ifndef _HAVE_NULL
+#define NULL    0
+#define _HAVE_NULL
+#endif
 
-
-#include <stddef.h>
-
-
+/* size_t is needed */
+#ifndef _HAVE_size_t
+#define _HAVE_size_t
+typedef unsigned size_t;
+#endif
 
 char* __fastcall__ strcat (char* dest, const char* src);
 char* __fastcall__ strchr (const char* s, int c);
@@ -90,6 +96,5 @@ const char* __fastcall__ _stroserror (unsigned char errcode);
 /* Map an operating system error number to an error message. */
 
 
-
 /* End of string.h */
 #endif