Fix up a few statistics problems.

Fix up a few statistics problems.
Stats pretty much line up with old code, except:
- bug in old code included L1 latency in L2 miss time, making it too high
- UniCoherence did cache-to-cache transfers even from non-owner caches,
so occasionally the icache would get a block from the dcache not the L2
- L2 can now receive ReadExReq from L1 since L1s have coherence

--HG--
extra : convert_revision : 5052c1a1767b5a662f30a88f16012165a73b791c