[parser] report better errors for multiple ForBindings in ForIn/Of loops

src/messages.js

Index: src/messages.js
diff --git a/src/messages.js b/src/messages.js
index e7e0938d56a8f6b117e10120ef029529e5f80062..72637fb76e6abadbb214a41e07c3349c26b8ec6c 100644
--- a/src/messages.js
+++ b/src/messages.js
@@ -199,7 +199,8 @@ var kMessages = {
   constructor_noncallable:       ["Class constructors cannot be invoked without 'new'"],
   array_not_subclassable:        ["Subclassing Arrays is not currently supported."],
   for_in_loop_initializer:       ["for-in loop variable declaration may not have an initializer."],
-  for_of_loop_initializer:       ["for-of loop variable declaration may not have an initializer."]
+  for_of_loop_initializer:       ["for-of loop variable declaration may not have an initializer."],
+  for_inof_loop_multi_bindings:  ["Invalid left-hand side in ", "%0", " loop: Must have a single binding."]
 };