Parser incorrectly accepts elements without closing tags

[tfausak]

I expected this parse to fail, but it succeeded:

Text.XML.Light.parseXMLDoc "<invalid-xml>"
-- Just Element
--   { elName = QName { qName = "invalid-xml" , qURI = Nothing , qPrefix = Nothing }
--   , elAttribs = []
--   , elContent = []
--   , elLine = Just 1
--   }