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/scheme/decompile-tree-il.scm

@@ -432,11 +432,6 @@
          `(call-with-values (lambda () ,@(recurse-body exp))
             ,(recurse (make-lambda #f '() body))))
 
-        ((<dynwind> body winder unwinder)
-         `(dynamic-wind ,(recurse winder)
-                        (lambda () ,@(recurse-body body))
-                        ,(recurse unwinder)))
-
         ((<dynlet> fluids vals body)
          `(with-fluids ,(map list
                              (map recurse fluids)
@@ -761,10 +756,6 @@
              (primitive 'call-with-values)
              (recurse exp) (recurse body))
 
-            ((<dynwind> winder body unwinder)
-             (primitive 'dynamic-wind)
-             (recurse winder) (recurse body) (recurse unwinder))
-
             ((<dynlet> fluids vals body)
              (primitive 'with-fluids)
              (for-each recurse fluids)