* gc.c: fix oldgen/remembered_shady counting algorithm.
* gc.c (rgengc_check_shady): increment
  `objspace->rgengc.remembered_shady_object_count' here.
* gc.c (rgengc_remember): return FALSE if obj is already remembered.
* gc.c (rgengc_rememberset_mark): make it void.
* gc.c (gc_mark_children): fix to double counting oldgen_object_count
  at minor GC.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41614 b2dd03c8-39d4-4d8f-98ff-823fe69b080e