Merge changes made in Gnus trunk.

Merge changes made in Gnus trunk.

nndraft.el (nndraft-request-expire-articles): Use the group name instead if "nndraft".
gnus.texi (Using IMAP): Remove the @acronyms from the headings.
nnregistry.el: Added.
nnimap.el (nnimap-insert-partial-structure): Be way more permissive when interpreting the structures.
GNUS-NEWS: Minor error in GNUS-NEWS - password-cache.el.
nnimap.el (nnimap-request-accept-article): Add \r\n to the lines to make this work with Cyrus.
gnus-registry.el: Don't prompt on load, which makes it impossible to build Gnus.
gnus-gravatar.el: Add gnus-gravatar-properties.
gnus-agent.el, gnus-art.el, gnus-bookmark.el, gnus-dired.el, gnus-group.el,\
 gnus-int.el, gnus-msg.el, gnus-registry.el, gnus-score.el, gnus-srvr.el,\
 gnus-sum.el, gnus-topic.el, gnus-util.el, gnus.el, mm-decode.el, mm-util.el,\
 mm-view.el, mml-smime.el, mml.el, nnmairix.el, nnrss.el, smime.el:\
 Introduce gnus-completing-read.
gnus-util.el: Make completing-read function configurable.
gnus-util.el: Add requires and fix history for iswitchb.
webmail.el: Remove netscape/my-deja, since they no longer exist.
gnus.el (gnus-local-domain): Declare variable obsolete.
nnimap.el (nnimap-insert-partial-structure): Get the type from the correct slot, too.
pop3.el (pop3-send-streaming-command, pop3-stream-length): New variable.
nnimap.el (nnimap-open-connection): Revert the auto-network->starttls code.
nnimap.el (nnimap-request-set-mark): Erase the buffer before issuing commands.
nnimap.el (nnimap-split-rule): Mark as obsolete.
gnus-sum.el (gnus-valid-move-group-p): Make sure that `group' is a symbol.
nnimap.el (nnimap-split-incoming-mail): Allow `default' as nnimap-split-methods value.
nnimap.el (nnimap-request-article): Downcase the NILs so that they are nil.
nndoc.el (nndoc-retrieve-groups): New function.
gnus.texi: Fix Gravatar documentation.