SF patch 588728 (Nathan Srebro).

The __delete__ method wrapper for descriptors was not supported

(I added a test, too.)

2.2 bugfix candidate.
diff --git a/Misc/ACKS b/Misc/ACKS
index fa08b8a..6e48457 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -452,6 +452,7 @@
 Mark Summerfield
 Kalle Svensson
 Hajime Saitou
+Nathan Srebro
 RajGopal Srinivasan
 Jim St. Pierre
 Quentin Stafford-Fraser