When parsing NSXMLDocument, detect if workaround for error was effective 
When parsing NSXMLDocument, detect if workaround for error was effective 

Note : when used with the NSXMLDocumentTidyXML option, NSXMLDocument’s -initWithData:options:error: seems able to handle invalid characters.
The -preFlightValidation: routine reintroduced for handling issue #507 isn’t probably useful anymore.
tothgy/vienna-rss,iamjasonchoi/vienna-rss,iamjasonchoi/vienna-rss,dak180/vienna,barijaona/vienna-rss,barijaona/vienna-rss,tothgy/vienna-rss,josh64x2/vienna-rss,dak180/vienna,ViennaRSS/vienna-rss,ViennaRSS/vienna-rss,lapcat/vienna-rss,tothgy/vienna-rss,josh64x2/vienna-rss,Eitot/vienna-rss,Eitot/vienna-rss,barijaona/vienna-rss,Eitot/vienna-rss,ViennaRSS/vienna-rss,barijaona/vienna-rss,barijaona/vienna-rss,ViennaRSS/vienna-rss,josh64x2/vienna-rss,lapcat/vienna-rss,dak180/vienna,josh64x2/vienna-rss,Eitot/vienna-rss,ViennaRSS/vienna-rss,tothgy/vienna-rss,iamjasonchoi/vienna-rss,lapcat/vienna-rss,dak180/vienna,lapcat/vienna-rss,josh64x2/vienna-rss