Also performed misc. cleanup, corrected use of temp variables in (let ...),
changed make-bindings-unique to preserve original names as prefixes, improved
detection of unused %set! forms in reduce-set!, and fixed map-variables to
extract the real value from (quote ...) literal forms.
With this change, any (%bind) returned from (simplify-let) or (simplify-form)
can be assumed to be flat, with unique bound symbols. Before, this was only
true of (%lambda) forms and the output of (compile).
Exception is (%tail-call ...) form, which is permitted simply because
(%tail-call ...) transfers control unidirectionally; the enclosing
(%set! ...) form wouldn't be run anyway.
Jesse D. McDonald