GROOVY-7607: Upgrade Log4J2 to 2.3
GROOVY-7607: Upgrade Log4J2 to 2.3

Downgrade to 2.3 as upgrade to 2.4 is not possible, because it requires at least Java 7.

paplorinc/incubator-groovy,apache/groovy,alien11689/incubator-groovy,graemerocher/incubator-groovy,avafanasiev/groovy,alien11689/incubator-groovy,alien11689/incubator-groovy,taoguan/incubator-groovy,traneHead/groovy-core,fpavageau/groovy,eginez/incubator-groovy,yukangguo/incubator-groovy,paplorinc/incubator-groovy,tkruse/incubator-groovy,bsideup/incubator-groovy,shils/groovy,ebourg/incubator-groovy,apache/incubator-groovy,jwagenleitner/incubator-groovy,apache/incubator-groovy,shils/groovy,tkruse/incubator-groovy,paplorinc/incubator-groovy,jwagenleitner/incubator-groovy,avafanasiev/groovy,yukangguo/incubator-groovy,upadhyayap/incubator-groovy,eginez/incubator-groovy,fpavageau/groovy,paulk-asert/incubator-groovy,jwagenleitner/groovy,apache/incubator-groovy,traneHead/groovy-core,armsargis/groovy,paulk-asert/groovy,dpolivaev/groovy,jwagenleitner/groovy,fpavageau/groovy,armsargis/groovy,gillius/incubator-groovy,paplorinc/incubator-groovy,i55ac/incubator-groovy,jwagenleitner/incubator-groovy,taoguan/incubator-groovy,sagarsane/incubator-groovy,ebourg/incubator-groovy,dpolivaev/groovy,bsideup/groovy-core,ebourg/incubator-groovy,alien11689/incubator-groovy,shils/incubator-groovy,jwagenleitner/groovy,tkruse/incubator-groovy,paulk-asert/incubator-groovy,graemerocher/incubator-groovy,traneHead/groovy-core,bsideup/incubator-groovy,paulk-asert/groovy,eginez/incubator-groovy,russel/incubator-groovy,paulk-asert/incubator-groovy,apache/groovy,sagarsane/incubator-groovy,russel/groovy,pledbrook/incubator-groovy,upadhyayap/incubator-groovy,russel/incubator-groovy,shils/groovy,gillius/incubator-groovy,eginez/incubator-groovy,avafanasiev/groovy,ebourg/incubator-groovy,bsideup/groovy-core,gillius/incubator-groovy,sagarsane/incubator-groovy,avafanasiev/groovy,shils/incubator-groovy,yukangguo/incubator-groovy,tkruse/incubator-groovy,shils/incubator-groovy,dpolivaev/groovy,paulk-asert/incubator-groovy,taoguan/incubator-groovy,i55ac/incubator-groovy,dpolivaev/groovy,russel/incubator-groovy,yukangguo/incubator-groovy,shils/incubator-groovy,jwagenleitner/incubator-groovy,bsideup/incubator-groovy,apache/groovy,i55ac/incubator-groovy,paulk-asert/incubator-groovy,apache/incubator-groovy,upadhyayap/incubator-groovy,graemerocher/incubator-groovy,fpavageau/groovy,armsargis/groovy,gillius/incubator-groovy,i55ac/incubator-groovy,paulk-asert/groovy,shils/groovy,bsideup/groovy-core,graemerocher/incubator-groovy,pledbrook/incubator-groovy,taoguan/incubator-groovy,russel/groovy,bsideup/groovy-core,armsargis/groovy,sagarsane/incubator-groovy,apache/groovy,pledbrook/incubator-groovy,paulk-asert/groovy,russel/groovy,russel/groovy,russel/incubator-groovy,pledbrook/incubator-groovy,jwagenleitner/groovy,traneHead/groovy-core,bsideup/incubator-groovy,upadhyayap/incubator-groovy