Create ast/ and parsing/ subdirectories and move appropriate files

src/parsing/parameter-initializer-rewriter.h

 // Copyright 2015 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_PARAMETER_EXPRESSION_REWRITER_H_
-#define V8_PARAMETER_EXPRESSION_REWRITER_H_
+#ifndef V8_PARSING_PARAMETER_EXPRESSION_REWRITER_H_
+#define V8_PARSING_PARAMETER_EXPRESSION_REWRITER_H_
 
-#include "src/ast.h"
+#include "src/ast/ast.h"
 
 namespace v8 {
 namespace internal {
 
 
 void RewriteParameterInitializerScope(uintptr_t stack_limit,
                                       Expression* initializer, Scope* old_scope,
                                       Scope* new_scope);
 
 
 }  // namespace internal
 }  // namespace v8
 
-#endif  // V8_PARAMETER_EXPRESSION_REWRITER_H_
+#endif  // V8_PARSING_PARAMETER_EXPRESSION_REWRITER_H_