Introduce a BuiltinsConstructStub that sets up new.target and does a [[call]] per ES6 9.3.2

src/types.cc

Index: src/types.cc
diff --git a/src/types.cc b/src/types.cc
index b1002be26ae93f2bcf25cf6d8ba6453ef605484b..64c368c95514189c77ba0b60e298b3c9d1632a7f 100644
--- a/src/types.cc
+++ b/src/types.cc
@@ -244,6 +244,7 @@ TypeImpl<Config>::BitsetType::Lub(i::Map* map) {
     case JS_ITERATOR_RESULT_TYPE:
     case JS_WEAK_MAP_TYPE:
     case JS_WEAK_SET_TYPE:
+    case JS_PROMISE_TYPE:
       if (map->is_undetectable()) return kUndetectable;
       return kOtherObject;
     case JS_FUNCTION_TYPE: