* gc.c: count old/young objects more correctly.
* gc.c (RVALUE_DEMOTE_FROM_OLD): decrement old object count.
* gc.c (RVALUE_DEMOTE_FROM_YOUNG): decrement young object count.
* gc.c (rb_gc_resurrect): increment old object count.
* gc.c (gc_marks_body): should not add old object count.
  This code is completely my misunderstanding.
* gc.c (rb_gc_force_recycle): decrement young or old object count
  correctly.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46327 b2dd03c8-39d4-4d8f-98ff-823fe69b080e