Implement ES6 Array.prototype.toString behind --harmony-tostring

src/array.js

Index: src/array.js
diff --git a/src/array.js b/src/array.js
index c702d8caf3a53a02d191f9076d81ca4dd9a2245b..784f51f0e4419b4b6beec682c5eeda60b85bf345 100644
--- a/src/array.js
+++ b/src/array.js
@@ -361,7 +361,7 @@ function ArrayToString() {
     func = array.join;
   }
   if (!IS_SPEC_FUNCTION(func)) {
-    return %_CallFunction(array, NoSideEffectsObjectToString);
+    return %_CallFunction(array, DefaultObjectToString);
   }
   return %_CallFunction(array, func);
 }