give fmt-c a name for every parameter

fmt-c takes a parameter's name with `cadr', so an unnamed one handed
over bare lost its second word to it: `(* const char)' dropped its
star, and `(int)' had no second word at all.

fmt-c-writer.scm

@@ -378,20 +378,21 @@ forms, and what remains."
   (if (named-arg? arg)
       (walk-type (maybe-unwrap-type (cdr arg)))
       ;; A lone type may arrive wrapped in parens of its own, and those
-      ;; are not part of it: ((* const char))
-      ;; Plain names e.g. (int) are left as is
-      (walk-type (if (and (pair? arg) (null? (cdr arg)) (pair? (car arg)))
-                     (car arg)
-                     arg))))
+      ;; are not part of it: ((* const char)), (int)
+      (walk-type (maybe-unwrap-type arg))))
 
+;;; A parameter reaches fmt-c as `(type name)' and nothing else: it
+;;; reads the name out with `cadr', so a nameless one is the type and
+;;; an explicit #f. Handing it the bare type instead made it read the
+;;; type's own second word as the name -- `(* const char)' lost its
+;;; star -- and a one-word type had no second word to read at all.
 (define (walk-arglist form)
   ;; E.g.:
   ;; ((float) (int) (const char) (* const char) (¤ (* const struct res) 32))
   ;; ((f1 float) (f2 float) (f3 float) (res (¤ float 4)))
   (map (lambda (arg)
-         (if (named-arg? arg)
-             (list (arg-type arg) (walk-type (car arg)))
-             (arg-type arg)))
+         (list (arg-type arg)
+               (and (named-arg? arg) (walk-type (car arg)))))
        (remove comment-form? form)))
 
 (define (walk-arg-types form)