[imp] Webmail attachment notification

[Chuck Hagenbuch]

Quoting Kevin Konowalec <webadmin at ualberta.ca>:

> Boy 4.2 sounds like a massive improvement over 4.1.x.  Will there be
> documentation available detailing all the new features and how to use
> them for maximum performance?

Mostly there is the changelog (docs/CHANGES), but there is already  
this blurb from docs/UPGRADING:

New Message List Format Hook
----------------------------

The new hook ``_imp_hook_msglist_format()`` has been added which allows the
formatting of a message entry in the mailbox message list to be altered
at the time the list is created.  This hook has made the following
configuration options obsolete::

    $conf['mailbox']['show_attachments']
    $conf['mailbox']['show_xpriority']

If you wish to continue using the functionality previously provided by these
options, you should activate the msglist_format hook in ``config/conf.php``.
The sample hook contained in ``config/hooks.php`` contains the code necessary
to replicate the previous behavior.

-chuck