Add Gregory K. Johnson's revised version of mailbox.py (funded by

the 2005 Summer of Code).

The revision adds a number of new mailbox classes that support adding
and removing messages; these classes also support mailbox locking and
default to using email.Message instead of rfc822.Message.

The old mailbox classes are largely left alone for backward compatibility.
The exception is the Maildir class, which was present in the old module
and now inherits from the new classes.  The Maildir class's interface
is pretty simple, though, so I think it'll be compatible with existing
code.

(The change to the NEWS file also adds a missing word to a different
news item, which unfortunately required rewrapping the line.)

Misc/ACKS

@@ -313,6 +313,7 @@ Drew Jenkins
 Flemming Kjr Jensen
 Jiba
 Orjan Johansen
+Gregory K. Johnson
 Simon Johnston
 Evan Jones
 Richard Jones

Misc/NEWS

@@ -99,6 +99,10 @@ Library
   as ``walk_packages()`` to support working with packages that are either
   in the filesystem or zip files.
 
+- The mailbox module can now modify and delete messages from
+  mailboxes, in addition to simply reading them.  Thanks to Gregory
+  K. Johnson for writing the code, and to the 2005 Google Summer of
+  Code for funding his work.
 
 - The ``__del__`` method of class ``local`` in module ``_threading_local``
   returned before accomplishing any of its intended cleanup.
@@ -202,8 +206,8 @@ Core and builtins
   especially long-running applications that, from time to time, temporarily
   use a large number of small objects.  Note that when Python returns an
   arena to the platform C's ``free()``, there's no guarantee that the
-  platform C will in turn return that memory to the operating system.  The
-  effect of the patch is to stop making that impossible, and in tests it
+  platform C library will in turn return that memory to the operating system.
+  The effect of the patch is to stop making that impossible, and in tests it
   appears to be effective at least on Microsoft C and gcc-based systems.
   Thanks to Evan Jones for hard work and patience.