* gc.c (make_deferred): Refactoring. Collect codes which should be
	  atomic.

	* gc.c (make_io_deferred, obj_free, rb_objspace_call_finalizer,
	  gc_page_sweep): Correspond to the above.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43506 b2dd03c8-39d4-4d8f-98ff-823fe69b080e