More improvements to DEFINE-HASH-CACHE / DEFUN-CACHED
- The :DEFAULT and :INIT-WRAPPER options are eliminated.
- Any cache is immediately usable in cold-init.
(Whether the underlying function works is a different issue)
- The memoization wrapper is a little faster on a miss
by avoiding recomputation of the hash for the missing entry.
- To update a 1-arg/1-result function in the cache costs only 1 cons
versus formerly 4 words for a 2-vector.