* gnus.el: Fix cycle in eager macroexpansion

* gnus.el: Fix cycle in eager macroexpansion

* lisp/gnus/gnus-sum.el (gnus-data): Use cl-defstruct.
(gnus-data-set-pos, gnus-data-set-header, gnus-data-set-mark)
(gnus-data-set-number): Delete macros; use `setf` instead.
(gnus-data-unread-p, gnus-data-read-p, gnus-data-pseudo-p, gnus-data-find)
(gnus-summary-skip-intangible, gnus-summary-article-number):
Redefine as inlinable functions rather than macros.

* lisp/gnus/gnus.el: Adjust autoloads for the macros turned functions.