Fixed shared_library build on Windows.

include/v8.h

 // 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:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 801 matching lines @@
 
   friend class ImplementationUtilities;
 };
 
 
 /**
  * A simple Maybe type, representing an object which may or may not have a
  * value.
  */
 template<class T>
-struct Maybe {
+struct V8_EXPORT Maybe {
   Maybe() : has_value(false) {}
   explicit Maybe(T t) : has_value(true), value(t) {}
   Maybe(bool has, T t) : has_value(has), value(t) {}
 
   bool has_value;
   T value;
 };
 
 
 // --- Special objects ---
@@ skipping 5598 matching lines @@
  */
 
 
 }  // namespace v8
 
 
 #undef TYPE_CHECK
 
 
 #endif  // V8_H_