Remove with-fluids; replaced by with-fluid* and inlined push-fluid primops

* libguile/vm-i-system.c (push-fluid, pop-fluid):
* doc/ref/vm.texi (Dynamic Environment Instructions): Rename wind-fluids
  to push-fluid, and unwind-fluids to pop-fluid.  They now only work on
  one fluid binding at a time.

* module/ice-9/boot-9.scm (with-fluid*): Implement in Scheme in terms of
  primcalls to push-fluid and pop-fluid.
  (custom-throw-handler, catch, with-throw-handler): Use with-fluid*
  instead of with-fluids, as with-fluids is no longer available before
  psyntax is loaded.
  (with-fluids): Define in Scheme in terms of with-fluid*.

* libguile/fluids.c (scm_with_fluid): Rename from scm_with_fluids, and
  don't expose to Scheme.

* libguile/eval.c (eval): Remove SCM_M_WITH_FLUIDS case.
* libguile/expand.c (expand_with_fluids): Remove with-fluids syntax.
  (DYNLET): Remove, no longer defining dynlet in the %expanded-vtables.
* libguile/expand.h: Remove dynlet definitions.
* module/ice-9/eval.scm (primitive-eval): Remove with-fluids case.
* libguile/memoize.c (do_push_fluid, do_pop_fluid): New primitive
  helpers, like wind and unwind.
  (memoize): Memoize wind and unwind primcalls.  Don't memoize dynlet to
  with-fluids.
  (scm_init_memoize): Initialize push_fluid and pop_fluid here.
* libguile/memoize.h (SCM_M_WITH_FLUIDS): Remove definition.

* module/ice-9/psyntax.scm (build-dynlet): Remove; this just supported
  with-fluids, which is now defined in boot-9.
* module/ice-9/psyntax-pp.scm: Regenerate.

* doc/ref/compiler.texi (Tree-IL):
* module/language/tree-il.scm:
* module/language/tree-il/analyze.scm:
* module/language/tree-il/canonicalize.scm:
* module/language/tree-il/compile-glil.scm:
* module/language/tree-il/cse.scm:
* module/language/tree-il/debug.scm:
* module/language/tree-il/effects.scm: Remove <dynlet>.  Add cases for
  primcalls to push-fluid and pop-fluid in compile-glil.scm and
  effects.scm.

* module/language/tree-il/peval.scm (peval): Factor out
  with-temporaries; probably a bad idea, but works for now.  Factor out
  make-begin0 (a better idea).  Inline primcalls to with-fluid*, and
  remove dynlet cases.

* module/language/tree-il/primitives.scm (*interesting-primitive-names*):
  Add with-fluid*.

doc/ref/compiler.texi

@@ -458,14 +458,6 @@ original binding names, @var{gensyms} are gensyms corresponding to the
 A version of @code{<let>} that creates recursive bindings, like
 Scheme's @code{letrec}, or @code{letrec*} if @var{in-order?} is true.
 @end deftp
-@deftp {Scheme Variable} <dynlet> fluids vals body
-@deftpx {External Representation} (dynlet @var{fluids} @var{vals} @var{body})
-Dynamic binding; the equivalent of Scheme's @code{with-fluids}.
-@var{fluids} should be a list of Tree-IL expressions that will
-evaluate to fluids, and @var{vals} a corresponding list of expressions
-to bind to the fluids during the dynamic extent of the evaluation of
-@var{body}.
-@end deftp
 @deftp {Scheme Variable} <prompt> tag body handler
 @deftpx {External Representation} (prompt @var{tag} @var{body} @var{handler})
 A dynamic prompt. Instates a prompt named @var{tag}, an expression,

doc/ref/vm.texi

@@ -1120,18 +1120,17 @@ wind/unwind thunk pair. @code{unwind} instructions should be properly
 paired with their winding instructions, like @code{wind}.
 @end deffn
 
-@deffn Instruction wind-fluids n
-Pop off @var{n} values and @var{n} fluids from the stack, in that order.
-Set the fluids to the values by creating a with-fluids object and
-pushing that object on the dynamic stack. @xref{Fluids and Dynamic
-States}.
+@deffn Instruction push-fluid
+Pop a value and a fluid from the stack, in that order.  Set the fluid
+to the value by creating a with-fluids object and pushing that object
+on the dynamic stack. @xref{Fluids and Dynamic States}.
 @end deffn
 
-@deffn Instruction unwind-fluids
+@deffn Instruction pop-fluid
 Pop a with-fluids object from the dynamic stack, and swap the current
 values of its fluids with the saved values of its fluids. In this way,
 the dynamic environment is left as it was before the corresponding
-@code{wind-fluids} instruction was processed.
+@code{wind-fluid} instruction was processed.
 @end deffn
 
 @deffn Instruction fluid-ref