Adds ApplyResult.discard and missing Pool._process_by_pid
Adds ApplyResult.discard and missing Pool._process_by_pid

andresriancho/billiard,djsmith42/billiard,djsmith42/billiard,andresriancho/billiard,flaviogrossi/billiard,pombredanne/billiard,jakirkham/billiard,flaviogrossi/billiard,jakirkham/billiard,pombredanne/billiard