[es8] Initial set of changes to support syntactic tail calls.

test/message/syntactic-tail-call-in-try-try-catch-finally.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 load(a, i) {
-  return a[i];
+// Flags: --harmony-explicit-tailcalls
+
+function f() {
+  return 1;
 }
 
-function f() {
-  return load(new Proxy({}, {}), undefined);
+function g() {
+  try {
+    try {
+      f();
+    } catch(e) {
+      return continue f();
+    }
+  } finally {
+    f();
+  }
 }
-
-f();
-f();
-load([11, 22, 33], 0);
-f();