8155992: Change name of StealRegionCompactionTask to something that emphasizes the compaction task.
Reviewed-by: kbarrett, ehelin, drwhite

8150994: UseParallelGC fails with UseDynamicNumberOfGCThreads with specjbb2005
Reviewed-by: tschatzl, kbarrett

8146987: Improve Parallel GC Full GC by caching results of live_words_in_range()
Summary: A large part of time in the parallel scavenge collector is spent finding out the amount of live words within memory ranges to find out where to move an object to. Try to incrementally calculate this value.
Reviewed-by: tschatzl, mgerdin, jmasa
Contributed-by: ray alex <sky1young@gmail.com>

8081382: Make flags ParallelGCThreads and ConcGCThreads of type uint
Reviewed-by: drwhite, stefank

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