Include wx/variant.h from wx/msw/ole/oleutils.h.

This ensures that this header is self-contained and can be included without
including wx/variant.h first.

Closes #16522.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_3_0_BRANCH@77526 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/ole/oleutils.h

@@ -21,6 +21,7 @@
 #include <ole2.h>
 #include "wx/intl.h"
 #include "wx/log.h"
+#include "wx/variant.h"
 
 // ============================================================================
 // General purpose functions and macros