* Add a result-type dependent DEFTRANSFORM which open-codes directly
to calls to REPLACE.
* Constant-fold the array reads for constant string arguments
in the transform (intended as a slezy benchmark trick, but actually
it looks as if having some literal strings mixed in with
variables is pretty common in real world CONCATENATE uses).
* Add transforms for REPLACE on mixed SIMPLE-BASE-STRINGS and
(SIMPLE-ARRAY CHARACTER (*)) to support.
* Speeds up a simple benchmark of concatenating two three-character
strings by a factor of 15, and by a factor of 30 when the strings
are constant. For a more real-world example, doing DIRECTORY on
a large set of files speeds up by 25%.
* Fix a broken test (extra close paren) that was uncovered by
the write-no-partial-fasls change.