test rename overhaul: step 8 - language tests

tests/language/src/StringInterpolation7Test.dart

-// Copyright (c) 2011, 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.
-
-// Dart test program testing string interpolation with toString on custom
-// classes and on null.
-
-
-class A {
-  const A();
-  String toString() { return "A"; }
-}
-
-class StringInterpolation7Test {
-
-  static testMain() {
-    A a = new A();
-    Expect.equals("A + A", "$a + $a");
-    a = null;
-    Expect.equals("null", "$a");
-  }
-}
-
-main() {
-  StringInterpolation7Test.testMain();
-}