Implement new Function.prototype.toString and fix CreateDynamicFunction parsing

src/messages.h

Index: src/messages.h
diff --git a/src/messages.h b/src/messages.h
index 221236d1db6c60e263e7b7b367bfccde9da375ed..e185bbbbe142097fc0d1981dd3fdd362082b5f37 100644
--- a/src/messages.h
+++ b/src/messages.h
@@ -596,6 +596,9 @@ class ErrorUtils : public AllStatic {
     "Setter function argument must not be a rest parameter")                   \
   T(ParamDupe, "Duplicate parameter name not allowed in this context")         \
   T(ParenthesisInArgString, "Function arg string contains parenthesis")        \
+  T(ArgStringTerminatesParametersEarly,                                        \
+    "Arg string terminates parameters early")                                  \
+  T(UnexpectedEndOfArgString, "Unexpected end of arg string")                  \
   T(RuntimeWrongNumArgs, "Runtime function given wrong number of arguments")   \
   T(SingleFunctionLiteral, "Single function literal required")                 \
   T(SloppyFunction,                                                            \