Patch from SF bug 570483 (Tim Northover).

In a fresh interpreter, type.mro(tuple) would segfault, because
PyType_Ready() isn't called for tuple yet.  To fix, call
PyType_Ready(type) if type->tp_dict is NULL.
diff --git a/Misc/ACKS b/Misc/ACKS
index c7da1b0..fb64941 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -336,6 +336,7 @@
 Hrvoje Niksic
 Bill Noon
 Stefan Norberg
+Tim Northover
 Joe Norton
 Neal Norwitz
 Jeffrey Ollie