:mod:`imaplib` now refreshes the cached capability list after a successful
:meth:`~imaplib.IMAP4.login` or :meth:`~imaplib.IMAP4.authenticate`, using
the ``CAPABILITY`` response sent by the server or, if none was sent, by
querying it, so that capabilities that become available only after
authentication (such as ``ENABLE`` on Gmail) are recognized.  Capabilities
advertised in the server greeting are now also used, avoiding a redundant
``CAPABILITY`` command.
