macro expanders return memoized expressions

* libguile/eval.c (scm_c_primitive_eval):
* module/ice-9/eval.scm (primitive-eval): Rely on the expander to
  produce a memoized expression. If the expression is already memoized,
  just pass it through (the equivalent of the old "noexpand" hack).

* libguile/memoize.c (scm_init_memoize): Initialize `memoize-expression'
  as the initial binding of `macroexpand'.

* libguile/modules.c (scm_module_transformer): Before modules are
  booted, look for `macroexpand', not `%pre-modules-transformer'.

* module/ice-9/boot-9.scm: No more %pre-modules-transformer. Loading
  psyntax extends `macroexpand'.
  (make-module): `macroexpand' is the default transformer.

* module/ice-9/psyntax.scm: No more `noexpand'.
  (top-level-eval-hook, local-eval-hook): Instead of annotating with
  noexpand, memoize the expression before handing it to primitive-eval.
  (macroexpand): No more noexpand hack -- in its place we have another
  hack, to memoize the result when running in eval mode.
* module/ice-9/psyntax-pp.scm: Regenerated.

libguile/memoize.c

@@ -1326,6 +1326,9 @@ scm_init_memoize ()
   scm_set_smob_print (scm_tc16_memoized, scm_print_memoized);
 
 #include "libguile/memoize.x"
+
+  scm_c_define ("macroexpand",
+                scm_variable_ref (scm_c_lookup ("memoize-expression")));
 }
 
 /*