7121618: Change type of number of GC workers to unsigned int.
Summary: Change variables representing the number of GC workers to uint from int and size_t. Change the parameter in work(int i) to work(uint worker_id).
Reviewed-by: brutisso, tonyp
7119027: G1: use atomics to update RS length / predict time of inc CSet
Summary: Make sure that the updates to the RS length and inc CSet predicted time are updated in an MT-safe way.
Reviewed-by: brutisso, iveresov