Migrated test block 23 to Dart 2.0.

tests/corelib_2/regexp/ranges-and-escaped-hyphens_test.dart

 // Copyright (c) 2014, the Dart project authors. All rights reserved.
 // Copyright 2013 the V8 project authors. All rights reserved.
 // Copyright (C) 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions
 // are met:
 // 1.  Redistributions of source code must retain the above copyright
 //     notice, this list of conditions and the following disclaimer.
 // 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 61 matching lines @@
   var regexp03a = new RegExp(r"[\--0]+").firstMatch(",-.01");
   shouldBe(regexp03a, ["-.0"]);
   var regexp03b = new RegExp(r"[+-\-]+").firstMatch("*+,-.");
   shouldBe(regexp03b, ["+,-"]);
 
   // The actual bug reported.
   var bug21232 =
       (new RegExp(r"^[,:{}\[\]0-9.\-+Eaeflnr-u \n\r\t]*$")).hasMatch('@');
   shouldBeFalse(bug21232);
 }