remove @apply memoizer

remove @apply memoizer

* libguile/memoize.c (memoize): Recognize a primcall to 'apply as
  SCM_M_APPLY.
  (@apply): Remove @apply memoizer.
  (unmemoize): Unmemoize using "apply", not "@apply".

* libguile/memoize.h:
* libguile/expand.c (scm_sym_atapply): Remove.

* module/ice-9/boot-9.scm (apply): Re-implement using apply primcall.
  Use case-lambda, so as to give an appropriate minimum arity.

* module/language/tree-il/compile-glil.scm (flatten-lambda-case):
  Compile a primcall of "apply" specially, not "@apply".

* module/language/tree-il/peval.scm (peval): Match primcalls to "apply",
  not "@apply".  Residualize "apply" primcalls.

* module/language/tree-il/primitives.scm (*interesting-primitive-names*):
  (*multiply-valued-primitives*): Remove @apply, and apply primitive
  expander.

* test-suite/tests/peval.test:
* test-suite/tests/tree-il.test: Update tests to expect residualized
  "apply".

* test-suite/tests/procprop.test ("procedure-arity"): Update test for
  better apply arity.

* test-suite/tests/strings.test ("string"): Update expected error.