winex11: Add infrastructure for managing the extra data of generic extension events.
diff --git a/configure.ac b/configure.ac
index 21c8d85..e82d193 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1045,7 +1045,7 @@
                          [libxcomposite ${notice_platform}development files not found, Xcomposite won't be supported.])
 
         dnl *** Check for XICCallback struct
-        AC_CHECK_MEMBERS([XICCallback.callback],,,
+        AC_CHECK_MEMBERS([XICCallback.callback, XEvent.xcookie],,,
 [#ifdef HAVE_X11_XLIB_H
 #include <X11/Xlib.h>
 #endif])