* gnus.texi (Agent Regeneration): New node.
(gnus-select-article-hook): clarified.
(gnus-downloaded-mark): Added definition.
(gnus-undownloaded-mark): Updated definition to reference the new
%O spec.
(gnus-agent-catchup): Identified articles that are NOT marked as read.
(gnus-agent-fetch-group): New command.
(gnus-agent-fetch-series): New command.
(Agent Expiry): Added comment to document that
gnus-request-expire-articles may invoke gnus-agent-expire.
(gnus-agent-mark-unread-after-downloaded): New variable.
(gnus-agent-consider-all-articles): New variable.
(gnus-agent-max-fetch-size): New variable.