6864886: G1: rename -XX parameters related to update buffers
Summary: renaming a couple of update buffer-related parameters to make them more understandable and consistent.
Reviewed-by: iveresov, ysr
6862295: JDWP threadid changes during debugging session (leading to ingored breakpoints)
Summary: Correctly count full GC operations for framework collectors. Add ForceFullGCJVMTIEpilogues as a future work around if needed.
Reviewed-by: jcoomes, alanb, ysr