[NaCl SDK] Add nacl_io and sdk_util namespaces.

native_client_sdk/src/libraries/sdk_util/simple_lock.h

 /* Copyright (c) 2013 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.
  */
 
 #ifndef LIBRARIES_SDK_UTIL_SIMPLE_LOCK_H_
 #define LIBRARIES_SDK_UTIL_SIMPLE_LOCK_H_
 
 #include "pthread.h"
 #include "sdk_util/macros.h"
 
+namespace sdk_util {
+
 /*
  * SimpleLock
  *
  * A pthread mutex object, with automatic initialization and destruction.
  * Should be used with AutoLock where possible.
  */
 class SimpleLock {
  public:
   SimpleLock() {
     pthread_mutex_init(&lock_, NULL);
   }
 
   ~SimpleLock() {
     pthread_mutex_destroy(&lock_);
   }
 
   pthread_mutex_t* mutex() const { return &lock_; }
 
  private:
   mutable pthread_mutex_t lock_;
 
   DISALLOW_COPY_AND_ASSIGN(SimpleLock);
 };
 
+}  // namespace sdk_util
+
 #endif  // LIBRARIES_SDK_UTIL_SIMPLE_LOCK_H_