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

native_client_sdk/src/libraries/nacl_io/kernel_wrap_glibc.cc

Index: native_client_sdk/src/libraries/nacl_io/kernel_wrap_glibc.cc
diff --git a/native_client_sdk/src/libraries/nacl_io/kernel_wrap_glibc.cc b/native_client_sdk/src/libraries/nacl_io/kernel_wrap_glibc.cc
index 308a0929ba48e93a4a40e436112b47eedf4a2922..b0e1c6c8a5685feac82c2c744ae9f2bca7fe277b 100644
--- a/native_client_sdk/src/libraries/nacl_io/kernel_wrap_glibc.cc
+++ b/native_client_sdk/src/libraries/nacl_io/kernel_wrap_glibc.cc
@@ -3,12 +3,12 @@
 // found in the LICENSE file.
 
 #include <sys/types.h>  // Include something that will define __GLIBC__.
+#include "nacl_io/kernel_wrap.h" // IRT_EXT is turned on in this header.
 
 // The entire file is wrapped in this #if. We do this so this .cc file can be
 // compiled, even on a non-glibc build.
-#if defined(__native_client__) && defined(__GLIBC__)
-
-#include "nacl_io/kernel_wrap.h"
+#if !defined(__NACL_IO_IRT_EXT__) && defined(__native_client__) && \
+    defined(__GLIBC__)
 
 #include <alloca.h>
 #include <assert.h>