don't lose the contents of the combobox if it was set to a value not in a list and a popup has been opened and closed (patch 1883474)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_8_BRANCH@51616 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/choice.h

@@ -66,6 +66,8 @@ public:
                 const wxValidator& validator = wxDefaultValidator,
                 const wxString& name = wxChoiceNameStr);
 
+    virtual void SetLabel(const wxString& label);
+
     virtual void Delete(unsigned int n);
     virtual void Clear();