...as otherwise dynamic_cast<xmlsecurity::pdfio::PDFNameElement*>(...) in
xmlsecurity/qa/unit/pdfsigning/pdfsigning.cxx will fail at least on macOS,
causing CppunitTest_xmlsecurity_pdfsigning to fail.

Change-Id: I7c41c994a1e6145b4740a97ffe47d0c42c4e3ca0