[NaCl SDK]: nacl_io: add nacl_io_uninit function.

native_client_sdk/src/libraries/ppapi_simple/ps_main.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.
 
 #ifdef __native_client__
 #include <irt.h>
 #include <irt_ppapi.h>
 #endif
 
 #include <stdio.h>
@@ skipping 25 matching lines @@
   if (nacl_interface_query(NACL_IRT_PPAPIHOOK_v0_1, &hooks, sizeof(hooks)) ==
       sizeof(hooks)) {
     return PpapiPluginMain();
   }
 #else
 int main(int argc, char* argv[]) {
 #endif
   // By default, or if not running in the browser we simply run the main
   // entry point directly, on the main thread.
   nacl_io_init();
-  return PSUserMainGet()(argc, argv);
+  int rtn = PSUserMainGet()(argc, argv);
+  nacl_io_uninit();
+  return rtn;
 }