Do all parsing for try/catch destructuring inside the appropriate scopes

test/mjsunit/regress/regress-5106.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.
+
+function* g1() {
+  try {
+    throw {};
+  } catch ({a = class extends (yield) {}}) {
+  }
+}
+g1().next();  // crashes without fix
+
+function* g2() {
+  let x = function(){};
+  try {
+    throw {};
+  } catch ({b = class extends x {}}) {
+  }
+}
+g2().next();  // crashes without fix
+
+function* g3() {
+  let x = 42;
+  try {
+    throw {};
+  } catch ({c = (function() { return x })()}) {
+  }
+}
+g3().next();  // throws a ReferenceError without fix