Fixed use of finalizers for guardians and SMOBs (undoes patches 23-24).

Fixed use of finalizers for guardians and SMOBs (undoes patches 23-24).

* libguile/gc.c (finalizer_trampoline): Removed.
  (scm_gc_register_finalizer): Removed (undoes patches 23 and 24).

* libguile/gc.h (scm_gc_register_finalizer): Removed.

* libguile/guardians.c (finalize_guarded): Undid patch 23.  Added support
  for "proxied finalizers".
  (scm_i_guard): Likewise.

* libguile/smob.c (scm_i_finalize_smob): Adapted to
  `GC_finalization_proc'.

* libguile/smob.h: Include <gc/gc.h>.
  (SCM_NEWSMOB): Use `GC_REGISTER_FINALIZER_NO_ORDER' instead of
  `scm_gc_register_finalizer ()'.
  (SCM_NEWSMOB3): Likewise.
  (scm_i_finalize_smob): Updated.

git-archimport-id: lcourtes@laas.fr--2005-libre/guile-core--boehm-gc--1.9--patch-29