Merge changes made in Gnus trunk.

Merge changes made in Gnus trunk.

nnimap.el (nnimap-finish-retrieve-group-infos): Return data in the nntp buffer so the agent can save it.
nnimap.el (nnimap-open-shell-stream): Bind `process-connection-type' to nil, so that CRLF doesn't get translated to \n; (nnimap-open-connection): Don't make 'shell commands only send \n.
nnimap.el (nnimap-request-group): Don't make `M-g' bug out on group with no marks.
gnus-agent.el (gnus-agent-load-alist): Nix out the alist if the file doesn't exist.
nnimap.el (nnimap-finish-retrieve-group-infos): Protect against groups that have no articles.
nnimap.el (nnimap-request-article): Check that we really got an article when we requested one.
gnus-html.el (gnus-html-schedule-image-fetching): Ignore all errors from url-retrieve, for instance about invalid URLs.
gnus-agent.el: Change default of gnus-agent-auto-agentize-methods to nil.