8067868: Add GCOld as a JTreg test Reviewed-by: kbarrett, dfazunen, ehelin

8048179: Early reclaim of large objects that are referenced by a few objects Summary: Push the remembered sets of large objects with few referenced into the dirty card queue at the beginning of the evacuation so that they may end up with zero remembered set entries at the end of the collection, and are potentially reclaimed. Also improve timing measurements of the early reclaim mechanism, and shorten flag names. Reviewed-by: brutisso, jmasa, dfazunen