* lisp/nnshimbun.el (top-level): Updated comments.

* lisp/nnshimbun.el (top-level): Updated comments.
(nnshimbun): New customize group.
(nnshimbun-keep-last-article): Defined as customize variable.
(nnshimbun-keep-unparsable-dated-articles): Ditto.
(nnshimbun-insert-nov): Use `when' instead of `if'.
(gnus-group-shimbun-server-history): Imported from
`gnus-group.el'.
(gnus-group-make-shimbun-group): Ditto.

* lisp/gnus-group.el (gnus-group-make-shimbun-group): Its real
definition is moved to `nnshimbun.el' and autload code is added.
(gnus-group-shimbun-server-history): Its definition is moved to
`nnshimbun.el'.