Fixed critical shutdown race in _Database._commit.
Related to SF patch 723231 (which pointed out the problem, but didn't
fix it, just shut up the warning msg -- which was pointing out a dead-
serious bug!).

Bugfix candidate.
diff --git a/Misc/NEWS b/Misc/NEWS
index b793a73..1098ad3 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -38,6 +38,14 @@
 Library
 -------
 
+- It's vital that a dumbdbm database be closed properly, else the
+  on-disk data and directory files can be left in mutually inconsistent
+  states.  dumbdbm.py's _Database.__del__() method attempted to close
+  the database properly, but a shutdown race in _Database._commit()
+  could prevent this form working, so that a program trusting __del__()
+  to get the on-disk files in synch could be badly surprised.  The race
+  has been repaired.
+
 - The classes in threading.py are now new-style classes.  That they
   weren't before was an oversight.