First pass at snooping stuff that compiles and doesn't break.

First pass at snooping stuff that compiles and doesn't break.

Still need:
-Handle NACK's on the recieve side
-Distinguish top level caches
-Handle repsonses from caches failing the fast path
-Handle BusError and propogate it
-Fix the invalidate packet associated with snooping in the cache

src/mem/bus.cc:
    Make sure to snoop on functional accesses
src/mem/cache/base_cache.cc:
    Wait to make a request into a response until it is ready to be issued
src/mem/cache/base_cache.hh:
    Support range changes for snoops
    Set up snoop responses for cache->cache transfers
src/mem/cache/cache_impl.hh:
    Only access the cache if it wasn't satisfied by cache->cache transfer
    Handle snoop phases (detect block, then snoop)
    Fix functional access to work properly (still need to fix snoop path for functional accesses)

--HG--
extra : convert_revision : 4c25f11d7a996c1f56f4f7b55dde87a344e5fdf8