6868991: JPRT: elide GCBasher_G1 test on winx64 until 6867250 is resolved Summary: JPRT: elide GCBasher_G1 test on winx64 until 6867250 is resolved Reviewed-by: jcoomes

6819077: G1: first GC thread coming late into the GC. Summary: The first worker thread is delayed when entering the GC because it clears the card count table that is used in identifying hot cards. Replace the card count table with a dynamically sized evicting hash table that includes an epoch based counter. Reviewed-by: iveresov, tonyp