dynamic-wind in terms of wind and unwind; remove <dynwind>, @dynamic-wind

* doc/ref/compiler.texi: Remove mention of <dynwind>.
* libguile/eval.c (eval): Remove SCM_M_DYNWIND case.
* libguile/expand.c: Remove scm_sym_at_dynamic_wind.
* libguile/memoize.c (do_wind, do_unwind): A couple of hacky subrs.  If
  we see a wind or unwind primcall, we expand to a call of a quoted subr
  value.  It works and removes a kind of memoized value from the
  interpreter.  For the compiler,primcalls to wind and unwind are
  handled specially.
  (MAKMEMO_DYNWIND): Remove.
  (scm_tc16_memoizer): Remove.  Yay!
  (memoize): Remove speculative lookup for toplevels to see if they are
  memoizers: there are no more memoizers.  Memoize calls to the wind and
  unwind primitives.
  (m_dynamic_wind): Remove.
  (unmemoize): Remove dynwind case.
  (scm_init_memoize): Add wind and unwind local definitions.

* module/ice-9/boot-9.scm (dynamic-wind): Reimplement in terms of "wind"
  and "unwind" primitives.  These primitives are not exposed to other
  modules.

* module/ice-9/eval.scm (primitive-eval): Remove dynwind case.
* module/language/scheme/decompile-tree-il.scm (do-decompile):
  (choose-output-names): Remove dynwind cases.

* module/language/tree-il.scm: Remove <dynwind>.  Yaaay!

* module/language/tree-il/analyze.scm (analyze-lexicals): Remove dynwind
  cases.

* module/language/tree-il/compile-glil.scm (*primcall-ops*): Add wind
  and unwind.
  (flatten-lambda-case): Remove dynwind case.  Yay!

* module/language/tree-il/cse.scm (cse):
* module/language/tree-il/debug.scm (verify-tree-il):
* module/language/tree-il/effects.scm (make-effects-analyzer):
* module/language/tree-il/peval.scm (singly-valued-expression?, peval):
  Remove <dywind> cases.  Inline primcalls to dynamic-wind.  Add
  constant folding for thunk?.

* module/language/tree-il/primitives.scm (*interesting-primitive-names*):
  Remove @dynamic-wind, and add procedure? and thunk?.
  (*effect+exception-free-primitives*): Add procedure? and thunk?.
  (*multiply-valued-primitives*): Remove @dynamic-wind.
  Remove @dynamic-wind expander.

* test-suite/tests/peval.test ("partial evaluation"): Update tests for
  dynwind desugaring.

module/language/tree-il.scm

@@ -46,7 +46,6 @@
             <letrec> letrec? make-letrec letrec-src letrec-in-order? letrec-names letrec-gensyms letrec-vals letrec-body
             <fix> fix? make-fix fix-src fix-names fix-gensyms fix-vals fix-body
             <let-values> let-values? make-let-values let-values-src let-values-exp let-values-body
-            <dynwind> dynwind? make-dynwind dynwind-src dynwind-winder dynwind-body dynwind-unwinder
             <dynlet> dynlet? make-dynlet dynlet-src dynlet-fluids dynlet-vals dynlet-body
             <dynref> dynref? make-dynref dynref-src dynref-fluid
             <dynset> dynset? make-dynset dynset-src dynset-fluid dynset-exp
@@ -136,7 +135,6 @@
 (define-type (<tree-il> #:common-slots (src) #:printer print-tree-il)
   (<fix> names gensyms vals body)
   (<let-values> exp body)
-  (<dynwind> winder body unwinder)
   (<dynref> fluid)
   (<dynset> fluid exp)
   (<prompt> tag body handler)
@@ -249,9 +247,6 @@
      (('let-values exp body)
       (make-let-values loc (retrans exp) (retrans body)))
 
-     (('dynwind winder body unwinder)
-      (make-dynwind loc (retrans winder) (retrans body) (retrans unwinder)))
-
      (('dynlet fluids vals body)
       (make-dynlet loc (map retrans fluids) (map retrans vals) (retrans body)))
 
@@ -339,11 +334,6 @@
     (($ <let-values> src exp body)
      `(let-values ,(unparse-tree-il exp) ,(unparse-tree-il body)))
 
-    (($ <dynwind> src winder body unwinder)
-     `(dynwind ,(unparse-tree-il winder)
-               ,(unparse-tree-il body)
-               ,(unparse-tree-il unwinder)))
-
     (($ <dynlet> src fluids vals body)
      `(dynlet ,(map unparse-tree-il fluids) ,(map unparse-tree-il vals)
               ,(unparse-tree-il body)))
@@ -424,10 +414,6 @@
               (($ <let-values> src exp body)
                (let*-values (((seed ...) (foldts exp seed ...)))
                  (foldts body seed ...)))
-              (($ <dynwind> src winder body unwinder)
-               (let*-values (((seed ...) (foldts winder seed ...))
-                             ((seed ...) (foldts unwinder seed ...)))
-                 (foldts body seed ...)))
               (($ <dynlet> src fluids vals body)
                (let*-values (((seed ...) (fold-values foldts fluids seed ...))
                              ((seed ...) (fold-values foldts vals seed ...)))
@@ -527,9 +513,6 @@ This is an implementation of `foldts' as described by Andy Wingo in
        (($ <let-values> src exp body)
         (make-let-values src (lp exp) (lp body)))
 
-       (($ <dynwind> src winder body unwinder)
-        (make-dynwind src (lp winder) (lp body) (lp unwinder)))
-
        (($ <dynlet> src fluids vals body)
         (make-dynlet src (map lp fluids) (map lp vals) (lp body)))