Merge changes made in Gnus trunk.

Merge changes made in Gnus trunk.

mail-parse.el (mail-header-encode-parameter): Use -encode-parameter instead of -encode-string.
nnimap.el (nnimap-fetch-inbox): Use "[]" as the parameter instead of "".
gnus-news.texi: Say what Emacs versions we support.
nnimap.el: Implement group deletion.
nnimap.el (nnimap-transform-headers): Return the size of the entire message in the Bytes header, not just the size of the first part.
gnus-news.texi: The nnimap makeover.
gnus-news.texi (Supported Emacs versions): Fix typo.
nnimap.el (nnimap-request-move-article): Fix article moving from nnimap to other servers.
nnimap.el (nnimap-request-set-mark): Don't wait for a response when we haven't requested anything.
nnimap.el (nnimap-command): Make sure that the error message doesn't error out.