SF patch 564549 (Erik Andersén).

The WeakKeyDictionary constructor didn't work when a dict arg was
given.  Fixed by moving a line.  Also adding a unit test.

Bugfix candidate.
diff --git a/Misc/ACKS b/Misc/ACKS
index 0adeec3..51807a7 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -16,6 +16,7 @@
 Billy G. Allie
 Mark Anacker
 Anders Andersen
+Erik Andersén
 Oliver Andrich
 Ross Andrus
 Jason Asbahr