serialize: bugfix literals named same as Object method defs
serialize: bugfix literals named same as Object method defs

nicola/rdflib.js,redaktor/rdflib.js,ariutta/rdflib.js,ariutta/rdflib.js,timbl/rdflib.js,nicola/rdflib.js,timbl/rdflib.js,ariutta/rdflib.js,redaktor/rdflib.js,timbl/rdflib.js