core: fix build

src/core/types.h

@@ -7,6 +7,7 @@
 
 #include "core/platform.h"
 #include <stdint.h>
+#include <stddef.h>
 
 #ifndef CROWN_DEBUG
 	#define CROWN_DEBUG 0
@@ -74,10 +75,6 @@ inline T clamp(T val, T mmin, T mmax)
 	#define __va_copy(dest, src) (dest = src)
 #endif
 
-#ifndef NULL
-	#define NULL 0
-#endif
-
 #define countof(arr) (sizeof(arr)/sizeof(arr[0]))
 #define container_of(ptr, type, member) ((char*)ptr - offsetof(type, member))