* ensures that when an item is added, if the number of unexpired items
>= maximum number of items specified, the oldest (based on ACCESS) is
expired
* when an item is "gotten", or "set", the access time is updated
The existing janitor system is unchanged, and used to actually delete
the items.
The only change from a consumer standpoint, is one addition parameter at
the end of a "New" call, that specifies the maximum number of items to
allow, or 0, if you want to disable the LRU at all.
