Converter + codetools: try to find out why FInterfaceIdentifierCache is Nil sometimes in TFindDeclarationTool.FindIdentifierInInterface.

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@41712 4005530d-fff6-0310-9dd1-cebe43e6787f
Converter: improve error handling in package conversion the same way project conversion has

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@41713 4005530d-fff6-0310-9dd1-cebe43e6787f