Root higher-order CPS term is always $kfun $cont

* module/language/cps/arities.scm:
* module/language/cps/closure-conversion.scm:
* module/language/cps/compile-bytecode.scm:
* module/language/cps/constructors.scm:
* module/language/cps/contification.scm:
* module/language/cps/cse.scm:
* module/language/cps/dce.scm:
* module/language/cps/elide-values.scm:
* module/language/cps/prune-bailouts.scm:
* module/language/cps/prune-top-level-scopes.scm:
* module/language/cps/renumber.scm:
* module/language/cps/self-references.scm:
* module/language/cps/simplify.scm:
* module/language/cps/specialize-primcalls.scm:
* module/language/tree-il/compile-cps.scm: Adapt to produce and consume
  raw $kfun $cont instances.

* .dir-locals.el: Update $letrec indentation.

module/language/cps/contification.scm

@@ -39,9 +39,7 @@
   #:export (contify))
 
 (define (compute-contification fun)
-  (let* ((dfg (match fun
-                (($ $fun free body)
-                 (compute-dfg body))))
+  (let* ((dfg (compute-dfg fun))
          (scope-table (make-hash-table))
          (call-substs '())
          (cont-substs '())
@@ -294,7 +292,7 @@
                 (visit-fun exp)))
            (_ #t)))))
 
-    (visit-fun fun)
+    (visit-cont fun)
     (values call-substs cont-substs fun-elisions cont-splices)))
 
 (define (apply-contification fun call-substs cont-substs fun-elisions cont-splices)
@@ -401,7 +399,7 @@
            (or (contify-call src proc args)
                (continue k src exp)))
           (_ (continue k src exp)))))))
-  (visit-fun fun))
+  (visit-cont fun))
 
 (define (contify fun)
   (call-with-values (lambda () (compute-contification fun))