Implement automatic loading of dart:core_native_fields library

bin/builtin.h

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef BIN_BUILTIN_H_
 #define BIN_BUILTIN_H_
 
 #include <stdio.h>
 #include <stdlib.h>
 
@@ skipping 16 matching lines @@
 
 #define UNIMPLEMENTED()                                                        \
   FATAL("unimplemented code")
 
 #define FUNCTION_NAME(name) Builtin_##name
 #define REGISTER_FUNCTION(name, count)                                         \
   { ""#name, FUNCTION_NAME(name), count },
 #define DECLARE_FUNCTION(name, count)                                          \
   extern void FUNCTION_NAME(name)(Dart_NativeArguments args);
 
-extern void Builtin_LoadLibrary();
+extern Dart_Handle Builtin_LoadLibrary();
 extern void Builtin_ImportLibrary(Dart_Handle library);
 extern void Builtin_SetNativeResolver();
 extern void PrintString(FILE* out, Dart_Handle object);
 
 #endif  // BIN_BUILTIN_H_