Result of add "unused-locals" compile arg to scalac

Try to add "unused-locals" compile arg to scalac and collect the warning informations, there are total 184 files and 296 compile warnings about  "unused-locals":

• core: 92 warnings
• mllib-local\mllib:  42 warnings
• graphx: 6 warnings
• streaming: 14 warnings
• Sql\hive\avro: 81 warnings
• Yarn\mesos\k8s: 23 warnings
• kafka: 3 warnings
• kinesis-asl: 4 warnings
• examples: 31  warnings