Disable the use of new style wxDirDialog under Vista.

IFileDialog-based dialog has a bug making it return a wrong path sometimes
under Vista, disable its use there to avoid it.

Closes #16005.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76152 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775