Implement handling of arrow functions in the parser

src/messages.js

Index: src/messages.js
diff --git a/src/messages.js b/src/messages.js
index 859bc0d721cd84bd9ba5bdd86b011b06d59dff8b..555f1f6d9564d2d2b62262288db4f82701fb9009 100644
--- a/src/messages.js
+++ b/src/messages.js
@@ -162,7 +162,8 @@ var kMessages = {
   symbol_to_primitive:           ["Cannot convert a Symbol wrapper object to a primitive value"],
   invalid_module_path:           ["Module does not export '", "%0", "', or export is not itself a module"],
   module_type_error:             ["Module '", "%0", "' used improperly"],
-  module_export_undefined:       ["Export '", "%0", "' is not defined in module"]
+  module_export_undefined:       ["Export '", "%0", "' is not defined in module"],
+  malformed_parameter_list:      ["Function parameter list is malformed"]
 };