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 e3d941b0395a94b93988a0e2d3ad69e56ae877e1..108f667dc956e0723415848e2d840f2b1d78f8d0 100644
--- a/src/messages.js
+++ b/src/messages.js
@@ -157,6 +157,7 @@ var kMessages = {
   strict_cannot_assign:          ["Cannot assign to read only '", "%0", "' in strict mode"],
   strict_poison_pill:            ["'caller', 'callee', and 'arguments' properties may not be accessed on strict mode functions or the arguments objects for calls to them"],
   strict_caller:                 ["Illegal access to a strict mode caller function."],
+  malformed_arrow_function_parameter_list: ["Malformed arrow function parameter list"],
   generator_poison_pill:         ["'caller' and 'arguments' properties may not be accessed on generator functions."],
   unprotected_let:               ["Illegal let declaration in unprotected statement context."],
   unprotected_const:             ["Illegal const declaration in unprotected statement context."],