test rename overhaul: step 3 _tests.dart => _test.dart

utils/tests/string_encoding/unicode_core_test.dart

 #!/usr/bin/env dart
 // Copyright (c) 2012, 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.
 
 #library("unicode_core_tests");
 #import("dunit.dart");
 #import("../../string_encoding/unicode_core.dart");
 
 void main() {
@@ skipping 85 matching lines @@
         "d800 dbff last byte missing");
 
     // impossible bytes
     Expect.listEquals([0xfffd], utf16CodeUnitsToCodepoints([0x110000]),
         "110000 out of bounds");
 
     // overlong sequences not possible in utf16 (nothing < x10000)
     // illegal code positions d800-dfff not encodable (< x10000)
   }
 }