letfn is a macro over a letfn* special form (Clojure semantics)

jolt modelled letfn as a special form directly, so (macroexpand-1 '(letfn …))
returned the form unchanged. Clojure's letfn is a macro that expands to letfn*,
and macroexpansion tooling (tools.macro, tools.analyzer) depends on that — its
special-form handlers key on letfn*, not letfn.

Split it the Clojure way:
- letfn* is now the special form (analyzer), taking flat name/fn-form pairs
  [name1 fn1 name2 fn2 …] — the letrec :let lowering is unchanged.
- letfn is a macro (00-syntax) turning each (name [params] body*) spec into a
  name + (fn name [params] body*) binding, so it expands to letfn*.

So (macroexpand-1 '(letfn [(f [x] x)] (f 1))) now yields
(letfn* [f (fn f [x] x)] (f 1)), and clojure.tools.macro passes its whole suite
(macrolet / symbol-macrolet / mexpand-all). Listed in docs + site.

make test green (+1 corpus row, 0 new divergences), shakesmoke byte-identical.
One re-mint (analyzer + the letfn macro); selfhost holds.

test/chez/corpus.edn

@@ -3379,4 +3379,5 @@
   {:suite "numbers / ^long is 64-bit" :label "^long comparison on a full-width long" :expected "false" :actual "((fn* ([^long a ^long b] (< a b))) 9223372036854775807 1)"}
   {:suite "numbers / ^long is 64-bit" :label "^long quot on a full-width long" :expected "3074457345618258602" :actual "((fn* ([^long a] (quot a 3))) 9223372036854775807)"}
   {:suite "host-interop / Compiler" :label "Compiler/specials keys include the special forms" :expected "true" :actual "(every? (set (keys clojure.lang.Compiler/specials)) (quote [if do let* fn* quote def loop* recur try letfn* var]))"}
+  {:suite "macros / letfn mutual recursion" :label "letfn binds mutually-recursive named fns" :expected "[true false]" :actual "(letfn [(ev? [n] (if (zero? n) true (od? (dec n)))) (od? [n] (if (zero? n) false (ev? (dec n))))] [(ev? 10) (ev? 7)])"}
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