[turbofan] fixed escape analysis bug: missing copy of virtual state

test/mjsunit/compiler/escape-analysis-framestate-use-at-branchpoint.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: --allow-natives-syntax --turbo --turbo-escape
+
+function foo() {
+  var o = {x:0};
+  for (var i = 0; o.x < 1;) {
+    o.x++;
+    i+= 1;
+  }
+ function bar() {i};
+ return o.x;
+}
+foo();
+foo();
+%OptimizeFunctionOnNextCall(foo);
+foo();