* gc.c: remove rb_objspace_t::marked_num.
  We can use `objspace_live_num()' instead of removed `marked_num'
  if it is after `after_gc_sweep()' function call.
* gc.c (after_gc_sweep): use objspace_live_num() instead of removed
  rb_objspace_t::marked_num.
* gc.c (gc_mark_ptr, gc_marks): remove rb_objspace_t::marked_num code.
* gc.c (gc_prepare_free_objects): do not call set_heaps_increment()
  with checking objspace->heap.marked_num. At this point, we only
  need to check availability of free-cell.
* gc.c (gc_prepare_free_objects):
* gc.c (lazy_sweep): call after_gc_sweep() if there are no sweep_able entry.
* gc.c (rest_sweep, gc_prepare_free_objects): remove after_gc_sweep() call.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@40702 b2dd03c8-39d4-4d8f-98ff-823fe69b080e