Move regexp implementation into its own folder.

src/regexp/regexp-stack.h

 // Copyright 2009 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.
 
-#ifndef V8_REGEXP_STACK_H_
-#define V8_REGEXP_STACK_H_
+#ifndef V8_REGEXP_REGEXP_STACK_H_
+#define V8_REGEXP_REGEXP_STACK_H_
+
+#include "src/allocation.h"
+#include "src/globals.h"
+#include "src/isolate.h"
 
 namespace v8 {
 namespace internal {
 
 class RegExpStack;
 
 // Maintains a per-v8thread stack area that can be used by irregexp
 // implementation for its backtracking stack.
 // Since there is only one stack area, the Irregexp implementation is not
 // re-entrant. I.e., no regular expressions may be executed in the same thread
@@ skipping 98 matching lines @@
 
   friend class ExternalReference;
   friend class Isolate;
   friend class RegExpStackScope;
 
   DISALLOW_COPY_AND_ASSIGN(RegExpStack);
 };
 
 }}  // namespace v8::internal
 
-#endif  // V8_REGEXP_STACK_H_
+#endif  // V8_REGEXP_REGEXP_STACK_H_