Implement operator== and hashCode for bound closures.

tests/language/local_function_non_equal_test.dart

+// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import "package:expect/expect.dart";
+
+foo() => () => 42;
+bar() {
+  var c = () => 54;
+  return c;
+}
+baz() {
+  c() => 68;
+  return c;
+}
+
+main() {
+  var first = foo();
+  var second = foo();
+  Expect.isFalse(identical(first, second));
+  Expect.notEquals(first, second);
+
+  first = bar();
+  second = bar();
+  Expect.isFalse(identical(first, second));
+  Expect.notEquals(first, second);
+
+  first = baz();
+  second = baz();
+  Expect.isFalse(identical(first, second));
+  Expect.notEquals(first, second);
+}