[strong] Implement static restrictions on binding/assignment to 'undefined' identifier.

src/ast-value-factory.h

Index: src/ast-value-factory.h
diff --git a/src/ast-value-factory.h b/src/ast-value-factory.h
index cb69579314c63ca5e9b398d294d7a3ddab69eb72..217858524b56cb1230bd768bbc5f7ae0c8dc0f58 100644
--- a/src/ast-value-factory.h
+++ b/src/ast-value-factory.h
@@ -265,6 +265,7 @@ class AstValue : public ZoneObject {
   F(this, "this")                                                          \
   F(throw_iterator_result_not_an_object, "ThrowIteratorResultNotAnObject") \
   F(to_string, "ToString")                                                 \
+  F(undefined, "undefined")                                                \
   F(use_asm, "use asm")                                                    \
   F(use_strong, "use strong")                                              \
   F(use_strict, "use strict")                                              \