Move more builtin files to strict mode.

src/regexp.js

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+"use strict";
+
 // This file relies on the fact that the following declaration has been made
 // in runtime.js:
 // var $Object = global.Object;
 // var $Array = global.Array;
 
 var $RegExp = global.RegExp;
 
 // -------------------------------------------------------------------
 
 // A recursive descent parser for Patterns according to the grammar of
@@ skipping 435 matching lines @@
 
   for (var i = 1; i < 10; ++i) {
     %DefineOrRedefineAccessorProperty($RegExp, '$' + i,
                                       RegExpMakeCaptureGetter(i), NoOpSetter,
                                       DONT_DELETE);
   }
   %ToFastProperties($RegExp);
 }
 
 SetUpRegExp();