[turbofan] Teach escape analysis about ObjectIsNaN.

test/mjsunit/regress/regress-crbug-698607.js

+// Copyright 2017 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
+
+function assertSame(expected, found) {
+  if (found === expected) {
+  } else if ((expected !== expected) && (found !== found)) {
+  }
+}
+
+function foo() {
+  var x = {var: 0.5};
+  assertSame(x, x.val);
+  return () => x;
+}
+
+foo(1);
+foo(1);
+%OptimizeFunctionOnNextCall(foo);
+foo(1);