added wxDP_SPIN/DROPDOWN styles (only Win32 native version implements the former)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@31498 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/datectlg.cpp

@@ -79,6 +79,9 @@ bool wxDatePickerCtrl::Create(wxWindow *parent,
                             long style,
                             const wxString& name)
 {
+    wxASSERT_MSG( !(style & wxDP_SPIN),
+                  _T("wxDP_SPIN style not supported, use wxDP_DEFAULT") );
+
     wxString txt;
     if (date.IsValid())
         txt = date.FormatDate();