Fix SF bug #474538: Memory (reference) leak in poller.register (Dave Brueck)

Replace some tortuous code that was trying to be clever but forgot to
DECREF the key and value, by more longwinded but obviously correct
code.

(Inspired by but not copying the fix from SF patch #475033.)
diff --git a/Misc/ACKS b/Misc/ACKS
index 18bac30..f6b73fe 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -54,6 +54,7 @@
 Dave Brennan
 Gary S. Brown
 Oleg Broytmann
+Dave Brueck
 Stan Bubrouski
 Erik de Bueger
 Jan-Hein B"uhrman