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

native_client_sdk/src/libraries/nacl_io/kernel_handle.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_NACL_IO_KERNEL_HANDLE_H_
 #define LIBRARIES_NACL_IO_KERNEL_HANDLE_H_
 
 #include <pthread.h>
 
 #include "nacl_io/ostypes.h"
-#include "utils/macros.h"
-#include "utils/ref_object.h"
+#include "sdk_util/macros.h"
+#include "sdk_util/ref_object.h"
 
 class Mount;
 class MountNode;
 
 // KernelHandle provides a reference counted container for the open
 // file information, such as it's mount, node, access type and offset.
 // KernelHandle can only be referenced when the KernelProxy lock is held.
 class KernelHandle : public RefObject {
  public:
   KernelHandle(Mount* mnt, MountNode* node, int oflags);
 
   off_t Seek(off_t offset, int whence);
 
   Mount* mount_;
   MountNode* node_;
   int mode_;
   size_t offs_;
 
  private:
   // May only be called by the KernelProxy when the Kernel's
   // lock is held.
   friend class KernelObject;
   friend class KernelProxy;
   void Acquire() { RefObject::Acquire(); }
   bool Release() { return RefObject::Release(); }
   DISALLOW_COPY_AND_ASSIGN(KernelHandle);
 };
 
 #endif  // LIBRARIES_NACL_IO_KERNEL_HANDLE_H_