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

native_client_sdk/src/libraries/nacl_io/mount_http.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_http.h"
 
 #include <assert.h>
 #include <ctype.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <stdio.h>
 #include <string.h>
 #include <sys/stat.h>
 #include <sys/types.h>
-#include <unistd.h>
 
 #include <vector>
 
 #include <ppapi/c/pp_errors.h>
 
 #include "nacl_io/mount_node_dir.h"
 #include "nacl_io/mount_node_http.h"
 #include "nacl_io/osinttypes.h"
+#include "nacl_io/osunistd.h"
 #include "sdk_util/auto_lock.h"
 
 namespace {
 
 typedef std::vector<char*> StringList_t;
 size_t SplitString(char* str, const char* delim, StringList_t* list) {
   char* item = strtok(str, delim);
 
   list->clear();
   while (item) {
@@ skipping 388 matching lines @@
   text[len] = 0;
 
   *out_manifest = text;
   return 0;
 }
 
 std::string MountHttp::MakeUrl(const Path& path) {
   return url_root_ +
          (path.IsAbsolute() ? path.Range(1, path.Size()) : path.Join());
 }