Add more mixin tests and start rejecting illegal syntax.

tests/language/mixin_illegal_syntax_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 M { }
+
+typedef T0 = abstract S with M;
+typedef T1 = final S with M;     /// 01: compile-time error
+typedef T2 = var S with M;       /// 02: compile-time error
+typedef T3 = const S with M;     /// 03: compile-time error
+typedef T4 = static S with M;    /// 04: compile-time error
+typedef T5 = external S with M;  /// 05: compile-time error
+
+class C0 extends abstract S with M { }  /// 06: compile-time error
+class C1 extends final S with M { }     /// 07: compile-time error
+class C2 extends var S with M { }       /// 08: compile-time error
+class C3 extends const S with M { }     /// 09: compile-time error
+class C4 extends static S with M { }    /// 10: compile-time error
+class C5 extends external S with M { }  /// 11: compile-time error
+
+class D0 extends S with M
+    implements M  /// 12: compile-time error
+    implements M { }
+
+class D1 extends T0 { }
+
+main() {
+  new T0();  /// 13: static type warning, runtime error
+  new T1();  /// 01: continued
+  new T2();  /// 02: continued
+  new T3();  /// 03: continued
+  new T4();  /// 04: continued
+  new T5();  /// 05: continued
+
+  new C0();  /// 06: continued
+  new C1();  /// 07: continued
+  new C2();  /// 08: continued
+  new C3();  /// 09: continued
+  new C4();  /// 10: continued
+  new C5();  /// 11: continued
+
+  new D0();  /// 12: continued
+  new D1();
+}