loplugin:constmethod in idl,helpcompiler

Change-Id: I9b328fc0a3ebdd15a646ee6dab800ffbadb1aaef
Reviewed-on: https://gerrit.libreoffice.org/44050
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

helpcompiler/source/BasCodeTagger.cxx

@@ -43,7 +43,7 @@ void LibXmlTreeWalker::ignoreCurrNodesChildren()
           m_Queue.pop_back();
 }
 
-bool LibXmlTreeWalker::end()
+bool LibXmlTreeWalker::end() const
 {
     return m_pCurrentNode->next == nullptr && m_Queue.empty();
 }