Suggested by degasus.

Only loop through and call getPointers when something has actually
changed.
Worth about 2-4% speedup un SMG over the previous commit.

Move ownership of cached_arraybases from CPMemory to VertexLoaderManager
to better match it usage.

Yet another story of games loading weird shit into registers.

For some reason, Burnout 2 would (in rare situations) load invalid
addresses into cp_state.array_bases. What would the real hardware
do in this situation? Who knows, Burnout 2 doesn't actually enable
the vertex array with the invalid address so nothing kinky happens.

But dolphin tries to optimise things and starts using the address
as soon as it is loaded into memory. This causes GetPointer (which is
now much more vocal) to throw an error.

The Fix:  We don't call GetPointer until we are sure the vertex array
has been enabled.

Disable bbox

VertexLoaderManager: reset stats properly