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
7123165: G1: output during parallel verification can get messed up
Summary: Serialize the worker threads that are generating output during parallel heap verification to make sure the output is consistent.
Reviewed-by: brutisso, johnc, jmasa