add stubs for XGL_WSI_X11
diff --git a/icd/intel/intel.h b/icd/intel/intel.h
index 115be85..2a29120 100644
--- a/icd/intel/intel.h
+++ b/icd/intel/intel.h
@@ -36,6 +36,7 @@
 
 #include <xgl.h>
 #include <xglDbg.h>
+#include <xglWsiX11Ext.h>
 
 #include "icd.h"
 #include "icd-bil.h"