Store i18n meta data in hidden symbols instead of js accessible properties

src/heap.h

Index: src/heap.h
diff --git a/src/heap.h b/src/heap.h
index 0f586e9284e5554a97911982c4c441dc2e44aaec..6792d8dc38cdd80a99a7725e72fc996f46afb5ec 100644
--- a/src/heap.h
+++ b/src/heap.h
@@ -376,7 +376,9 @@ namespace internal {
   V(next_string, "next")                                                 \
   V(byte_length_string, "byteLength")                                    \
   V(byte_offset_string, "byteOffset")                                    \
-  V(buffer_string, "buffer")
+  V(buffer_string, "buffer")                                             \
+  V(intl_initialized_marker_string, "v8::intl_initialized_marker")       \
+  V(intl_impl_object_string, "v8::intl_object")
 
 // Forward declarations.
 class GCTracer;