add alt popup window style allowing to use keyboard and comboboxes in the popup window and use it for the generic date picker (patch 1582391 from Jaakko)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@42247 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/datectlg.cpp

@@ -414,6 +414,10 @@ bool wxDatePickerCtrlGeneric::Create(wxWindow *parent,
 
     m_popup = new wxCalendarComboPopup();
 
+#if defined(__WXMSW__)
+    // without this keyboard navigation in month control doesn't work
+    m_combo->UseAltPopupWindow();
+#endif
     m_combo->SetPopupControl(m_popup);
 
     m_cal = m_popup;