checkstyle: bump to 6.18
checkstyle: bump to 6.18

workcraft/workcraft,danilovesky/workcraft,jrbeaumont/workcraft,tuura/workcraft,danilovesky/workcraft,danilovesky/workcraft,tuura/workcraft,workcraft/workcraft,tuura/workcraft,workcraft/workcraft,jrbeaumont/workcraft,danilovesky/workcraft,workcraft/workcraft,jrbeaumont/workcraft