GROOVY-8242: @Newify default attribute value (closes #579)
GROOVY-8242: @Newify default attribute value (closes #579)

Class values are only required for Python-style conversions so the
attribute should default to an empty array to indicate it is not
strictly required.

traneHead/groovy-core,russel/groovy,traneHead/groovy-core,paulk-asert/incubator-groovy,shils/groovy,avafanasiev/groovy,avafanasiev/groovy,jwagenleitner/incubator-groovy,shils/incubator-groovy,russel/incubator-groovy,traneHead/groovy-core,shils/incubator-groovy,armsargis/groovy,jwagenleitner/incubator-groovy,paulk-asert/groovy,jwagenleitner/incubator-groovy,apache/incubator-groovy,paulk-asert/groovy,paulk-asert/incubator-groovy,apache/incubator-groovy,paulk-asert/incubator-groovy,russel/incubator-groovy,paulk-asert/groovy,paulk-asert/incubator-groovy,avafanasiev/groovy,russel/incubator-groovy,shils/groovy,paulk-asert/groovy,russel/groovy,apache/groovy,jwagenleitner/groovy,apache/groovy,armsargis/groovy,traneHead/groovy-core,shils/incubator-groovy,apache/groovy,apache/incubator-groovy,avafanasiev/groovy,jwagenleitner/groovy,shils/groovy,jwagenleitner/incubator-groovy,apache/incubator-groovy,russel/incubator-groovy,shils/groovy,paulk-asert/incubator-groovy,russel/groovy,armsargis/groovy,russel/groovy,shils/incubator-groovy,apache/groovy,jwagenleitner/groovy,jwagenleitner/groovy,armsargis/groovy