Make generator constructors configurable

src/generator.js

Index: src/generator.js
diff --git a/src/generator.js b/src/generator.js
index 8e9ed8f2566a7e8088e8cb26e1018967d8d9d0f2..9ab7dcb9aab9b78baea82ca749ce129a5350be75 100644
--- a/src/generator.js
+++ b/src/generator.js
@@ -97,7 +97,7 @@ function SetUpGenerators() {
   %AddNamedProperty(GeneratorObjectPrototype, symbolIterator,
       GeneratorObjectIterator, DONT_ENUM | DONT_DELETE | READ_ONLY);
   %AddNamedProperty(GeneratorObjectPrototype, "constructor",
-      GeneratorFunctionPrototype, DONT_ENUM | DONT_DELETE | READ_ONLY);
+      GeneratorFunctionPrototype, DONT_ENUM | READ_ONLY);
   %AddNamedProperty(GeneratorObjectPrototype,
       symbolToStringTag, "Generator", DONT_ENUM | READ_ONLY);
   %InternalSetPrototype(GeneratorFunctionPrototype, $Function.prototype);
@@ -105,7 +105,7 @@ function SetUpGenerators() {
       symbolToStringTag, "GeneratorFunction", DONT_ENUM | READ_ONLY);
   %SetCode(GeneratorFunctionPrototype, GeneratorFunctionPrototypeConstructor);
   %AddNamedProperty(GeneratorFunctionPrototype, "constructor",
-      GeneratorFunction, DONT_ENUM | DONT_DELETE | READ_ONLY);
+      GeneratorFunction, DONT_ENUM | READ_ONLY);
   %InternalSetPrototype(GeneratorFunction, $Function);
   %SetCode(GeneratorFunction, GeneratorFunctionConstructor);
 }