Added support for NaCl IO to use the IRT Extension API.

native_client_sdk/src/libraries/nacl_io/kernel_wrap_dummy.cc

Index: native_client_sdk/src/libraries/nacl_io/kernel_wrap_dummy.cc
diff --git a/native_client_sdk/src/libraries/nacl_io/kernel_wrap_dummy.cc b/native_client_sdk/src/libraries/nacl_io/kernel_wrap_dummy.cc
index c4d0df8607039cbc471947fc99f975357a8372d9..1b878844d7ae91ff32f28ad35de325653d73598d 100644
--- a/native_client_sdk/src/libraries/nacl_io/kernel_wrap_dummy.cc
+++ b/native_client_sdk/src/libraries/nacl_io/kernel_wrap_dummy.cc
@@ -2,13 +2,16 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "nacl_io/kernel_wrap.h" // IRT_EXT is turned on in this header.
+
 // The Chromium build system defines __linux__ even for native client builds,
 // so guard against __native_client__ being defined as well.
-#if defined(WIN32) || (defined(__linux__) && !defined(__native_client__))
+#if defined(WIN32) || (!defined(__NACL_IO_IRT_EXT__) && \
+                       defined(__linux__) && \
+                       !defined(__native_client__))
 
 #include <errno.h>
 
-#include "nacl_io/kernel_wrap.h"
 #include "nacl_io/kernel_wrap_real.h"
 
 // "real" functions, i.e. the unwrapped original functions. For Windows/Linux