Age the number string cache so it does not keep strings

src/runtime.cc

Index: src/runtime.cc
===================================================================
--- src/runtime.cc	(revision 9686)
+++ src/runtime.cc	(working copy)
@@ -13336,6 +13336,13 @@
   return isolate->heap()->ToBoolean(obj1->map() == obj2->map());
 }
 
+RUNTIME_FUNCTION(MaybeObject*, Runtime_AreIdenticalObject) {
+  ASSERT(args.length() == 2);
+  Handle<Object> obj1(args[0]);
+  Handle<Object> obj2(args[1]);
+  return isolate->heap()->ToBoolean(*obj1 == *obj2);
+}
+
 // ----------------------------------------------------------------------------
 // Implementation of Runtime