Fix windows shared library build.

R=svenpanne@chromium.org

Review URL: https://chromiumcodereview.appspot.com/26814002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@17131 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

include/v8.h

@@ -847,7 +847,7 @@ class V8_EXPORT EscapableHandleScope : public HandleScope {
  * value.
  */
 template<class T>
-struct V8_EXPORT Maybe {
+struct Maybe {
   Maybe() : has_value(false) {}
   explicit Maybe(T t) : has_value(true), value(t) {}
   Maybe(bool has, T t) : has_value(has), value(t) {}