remove asubrs

remove asubrs

* libguile/tags.h (scm_tcs_subrs, scm_tc7_asubr): Remove definitions.

* libguile/goops.c (scm_class_of)
* libguile/procprop.c (scm_i_procedure_arity)
* libguile/procs.c (scm_thunk_p)
* libguile/vm.c (apply_foreign): Remove cases for asubrs.

* libguile/array-map.c: Gut all of the optimizations, because there are
  no more asubrs, soon won't be rpsubrs, and all of this should happen
  on the Scheme level, ideally.