bpo-39382: Avoid dangling object use in abstract_issubclass() (GH-18530)

Hold reference of __bases__ tuple until tuple item is done with, because by
dropping the reference the item may be destroyed.
diff --git a/Misc/ACKS b/Misc/ACKS
index f329a2d..fe24a56 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -594,6 +594,7 @@
 Jeroen Van Goey
 Christoph Gohlke
 Tim Golden
+Yonatan Goldschmidt
 Mark Gollahon
 Guilherme Gonçalves
 Tiago Gonçalves