Move thread_pool.h into utils so it can be shared by more than one example.

native_client_sdk/src/libraries/utils/auto_lock.h

-/* 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.
- */
-
-#ifndef LIBRARIES_UTILS_AUTO_LOCK_H_
-#define LIBRARIES_UTILS_AUTO_LOCK_H_
-
-#include <pthread.h>
-
-class AutoLock {
- public:
-  explicit AutoLock(pthread_mutex_t* lock) {
-    lock_ = lock;
-    pthread_mutex_lock(lock_);
-  }
-  ~AutoLock() {
-    if (lock_) pthread_mutex_unlock(lock_);
-  }
-
-  void Unlock() {
-    if (lock_) pthread_mutex_unlock(lock_);
-    lock_ = NULL;
-  }
-
- private:
-  pthread_mutex_t* lock_;
-};
-
-#endif  // LIBRARIES_UTILS_AUTO_LOCK_H_