* gc.c: change objspace::rgengc::parent_object_is_old (boolean)
  to objspace::rgengc::parent_object (VALUE).
  Use Qfalse or RVALUE pointer instead of FALSE and TRUE.
* gc.c (gc_marks_body): should clear parent_object just before
  gc_mark_roots() because there are no parents objects
  for root objects.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46939 b2dd03c8-39d4-4d8f-98ff-823fe69b080e