ES6: Implement Object.setPrototypeOf

src/messages.js

Index: src/messages.js
diff --git a/src/messages.js b/src/messages.js
index 20d5f991a547ad4514941c3043ef8982ab7e44ff..6cc9ad237364afc5f1cdd8d27caa826b105b2ed6 100644
--- a/src/messages.js
+++ b/src/messages.js
@@ -78,7 +78,7 @@ var kMessages = {
   getter_must_be_callable:       ["Getter must be a function: ", "%0"],
   setter_must_be_callable:       ["Setter must be a function: ", "%0"],
   value_and_accessor:            ["Invalid property.  A property cannot both have accessors and be writable or have a value, ", "%0"],
-  proto_object_or_null:          ["Object prototype may only be an Object or null"],
+  proto_object_or_null:          ["Object prototype may only be an Object or null: ", "%0"],
   property_desc_object:          ["Property description must be an object: ", "%0"],
   redefine_disallowed:           ["Cannot redefine property: ", "%0"],
   define_disallowed:             ["Cannot define property:", "%0", ", object is not extensible."],