[NaCl SDK] Add nacl_io and sdk_util namespaces.

native_client_sdk/src/libraries/nacl_io/path.cc

 /* Copyright (c) 2012 The Chromium Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #include "nacl_io/path.h"
 
 #include <stdio.h>
 #include <string.h>
 #include <string>
 
+namespace nacl_io {
+
 Path::Path() {}
 
 Path::Path(const Path& path) {
   paths_ = path.paths_;
 }
 
 Path::Path(const std::string& path) {
   Set(path);
 }
 
@@ skipping 174 matching lines @@
 
 Path& Path::operator =(const Path& p) {
   paths_ = p.paths_;
   return *this;
 }
 
 Path& Path::operator =(const std::string& p) {
   return Set(p);
 }
 
+}  // namespace nacl_io
+