Include what you use for the preparser.

src/unicode-inl.h

Index: src/unicode-inl.h
diff --git a/src/unicode-inl.h b/src/unicode-inl.h
index c0649d74fb051390f8633e836326517545830ccb..2827553bef356d8d7b0868e46441987c68244b9c 100644
--- a/src/unicode-inl.h
+++ b/src/unicode-inl.h
@@ -1,4 +1,4 @@
-// Copyright 2007-2010 the V8 project authors. All rights reserved.
+// Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -28,7 +28,9 @@
 #ifndef V8_UNICODE_INL_H_
 #define V8_UNICODE_INL_H_
 
-#include "unicode.h"
+#include "unicode.h"  // IWYU pragma: export
+
+#include <endian.h>
 
 namespace unibrow {