Improve strictness of Annex B 3.3 for generators and async functions

test/mjsunit/harmony/sloppy-no-duplicate-generators.js

+// Copyright 2016 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --harmony-restrictive-generators
+
+// Generators don't get sloppy-mode block-scoped function hoisting
+
+// No hoisting to the global scope
+
+{
+  function* foo() {}
+  assertEquals('function', typeof foo);
+}
+assertEquals('undefined', typeof foo);
+
+// No hoisting within a function scope
+(function() {
+  { function* bar() {} }
+  assertEquals('undefined', typeof bar);
+})();
+
+// Lexical shadowing allowed, no hoisting
+(function() {
+  function* x() { yield 1; }
+  { function* x() { yield 2 } }
+  assertEquals(1, x().next().value);
+})();