Merge branch 'qt_combobox_crash' of https://github.com/GeoTeric/wxWidgets

Fix crashes when using wxCB_READONLY in wxQt.

See https://github.com/wxWidgets/wxWidgets/pull/1221

include/wx/qt/combobox.h

@@ -87,6 +87,7 @@ protected:
 
 private:
     void SetActualValue(const wxString& value);
+    bool IsReadOnly() const;
 
     // From wxTextEntry:
     virtual wxWindow *GetEditableWindow() wxOVERRIDE { return this; }