RFR(M): 6921087: G1: remove per-GC-thread expansion tables from the fine-grain remembered sets

[John Cuthbertson]

Hi Everyone,

Can I have a review for the cleanup changes, supplied by Thomas Schatzl 
(Johannes Kepler University at Linz), for this CR? The webrev can be 
found at: http://cr.openjdk.java.net/~johnc/6921087/webrev.0/

Summary:
Thomas has removed the per thread expansion tables (PosParPRT) and 
associated, unused, expansion and compaction code along with some 
additional unused code. This change significantly reduces the code 
complexity of the fine grained RSet entries. These changes are a 
prerequisite for some other changes that Thomas has been working on to 
optimize the freeing of RSets' fine grained entries.

I've looked at the changes and they have a thumbs up from me.

Testing: OpenDS (performed by Thomas), the GC test suite with heap 
verification enabled (me), and jprt (me).

Thanks,

JohnC