8159073: : Error handling incomplete when creating GC threads lazily
Reviewed-by: drwhite, tschatzl, sangheki

8157240: GC task trace logging is incomprehensible
Reviewed-by: tschatzl, redestad

6858051: Create GC worker threads dynamically
Reviewed-by: tschatzl, drwhite

8138707: TestPromotionEventWithParallelScavenge.java crashes using undefined GC id.
Reviewed-by: mgerdin, jwilhelm

8138863: Refactor WaitForBarrierGCTask
Reviewed-by: mgerdin, jwilhelm

8138862: Remove some unused code and subclasses in gcTaskManager.hpp/cpp
Reviewed-by: mgerdin, jwilhelm

8079792: GC directory structure cleanup
Reviewed-by: brutisso, stefank, david