xmlsecurity: Log unknown xml elements for ooxml

Change-Id: I0daf81ac91da1d6206282e486298d059b937bb21
Reviewed-on: https://gerrit.libreoffice.org/40819
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Samuel Mehrbrodt <Samuel.Mehrbrodt@cib.de>

include/sal/log-areas.dox

@@ -530,6 +530,7 @@ certain functionality.
 @li @c xmlsecurity.comp - xml security component
 @li @c xmlsecurity.dialogs - xml security dialogs
 @li @c xmlsecurity.helper
+@li @c xmlsecurity.ooxml - OOXML signature support
 @li @c xmlsecurity.pdfio - signing of existing PDF
 @li @c xmlsecurity.xmlsec - xmlsec wrapper
 @li @c xmlsecurity.xmlsec.gpg - gpg xmlsec component

xmlsecurity/source/helper/ooxmlsecparser.cxx

@@ -120,6 +120,10 @@ void SAL_CALL OOXMLSecParser::startElement(const OUString& rName, const uno::Ref
         m_aCertDigest.clear();
         m_bInCertDigest = true;
     }
+    else
+    {
+        SAL_INFO("xmlsecurity.ooxml", "Unknown xml element: " << rName);
+    }
 
     if (m_xNextHandler.is())
         m_xNextHandler->startElement(rName, xAttribs);