Get the most basic mixin applications working.

tests/language/mixin_naming_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.
+
+class S { }
+class M1 { }
+class M2 { }
+class M3 { }
+
+typedef C = S with M1, M2, M3;
+
+class S_M1 { }
+class S_M1_M2 { }
+
+main() {
+  var c = new C();
+  Expect.isTrue(c is C);
+  Expect.isTrue(c is S);
+  Expect.isFalse(c is S_M1);
+  Expect.isFalse(c is S_M1_M2);
+
+  var sm = new S_M1();
+  Expect.isFalse(sm is C);
+  Expect.isFalse(sm is S);
+  Expect.isTrue(sm is S_M1);
+  Expect.isFalse(sm is S_M1_M2);
+
+  var smm = new S_M1_M2();
+  Expect.isFalse(smm is C);
+  Expect.isFalse(smm is S);
+  Expect.isFalse(smm is S_M1);
+  Expect.isTrue(smm is S_M1_M2);
+}