[NaCl SDK] Add nacl_io and sdk_util namespaces.

native_client_sdk/src/libraries/nacl_io/mount_passthrough.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/mount_passthrough.h"
 #include <errno.h>
 #include "nacl_io/kernel_wrap_real.h"
 
+namespace nacl_io {
+
 class MountNodePassthrough : public MountNode {
  public:
   explicit MountNodePassthrough(Mount* mount, int real_fd)
       : MountNode(mount), real_fd_(real_fd) {}
 
  protected:
   virtual Error Init(int flags) { return 0; }
 
   virtual void Destroy() {
     if (real_fd_)
@@ skipping 130 matching lines @@
 
 Error MountPassthrough::Rmdir(const Path& path) {
   return _real_rmdir(path.Join().c_str());
 }
 
 Error MountPassthrough::Remove(const Path& path) {
   // Not implemented by NaCl.
   return ENOSYS;
 }
 
+}  // namespace nacl_io
+