Move builtin JavaScript sources into own directory.

src/harmony-regexp.js

-// Copyright 2014 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.
-
-(function(global, utils) {
-
-'use strict';
-
-%CheckIsBootstrapping();
-
-// -------------------------------------------------------------------
-// Imports
-
-var GlobalRegExp = global.RegExp;
-
-// -------------------------------------------------------------------
-
-// ES6 draft 12-06-13, section 21.2.5.3
-// + https://bugs.ecmascript.org/show_bug.cgi?id=3423
-function RegExpGetFlags() {
-  if (!IS_SPEC_OBJECT(this)) {
-    throw MakeTypeError(kFlagsGetterNonObject, TO_STRING(this));
-  }
-  var result = '';
-  if (this.global) result += 'g';
-  if (this.ignoreCase) result += 'i';
-  if (this.multiline) result += 'm';
-  if (this.unicode) result += 'u';
-  if (this.sticky) result += 'y';
-  return result;
-}
-
-%DefineAccessorPropertyUnchecked(GlobalRegExp.prototype, 'flags',
-                                 RegExpGetFlags, null, DONT_ENUM);
-%SetNativeFlag(RegExpGetFlags);
-
-})