[NaCl SDK] Fix SDK waterfall: unistd.h does not exist on windows.

native_client_sdk/src/libraries/nacl_io/mount_dev.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.
  */
 #if defined(WIN32)
 #define _CRT_RAND_S
 #endif
 
 #include <errno.h>
 #include <fcntl.h>
 #include <string.h>
-#include <unistd.h>
 #include "nacl_io/kernel_wrap_real.h"
 #include "nacl_io/mount_dev.h"
 #include "nacl_io/mount_node.h"
 #include "nacl_io/mount_node_dir.h"
+#include "nacl_io/osunistd.h"
 #include "nacl_io/pepper_interface.h"
 #include "sdk_util/auto_lock.h"
 
 #if defined(__native_client__)
 #include <irt.h>
 #elif defined(WIN32)
 #include <stdlib.h>
 #endif
 
 namespace {
@@ skipping 318 matching lines @@
   INITIALIZE_DEV_NODE_1("/stderr", RealNode, 2);
 
   return 0;
 }
 
 void MountDev::Destroy() {
   if (root_)
     root_->Release();
   root_ = NULL;
 }