Rename `gnus-pull' to `gnus-alist-pull'.

Rename `gnus-pull' to `gnus-alist-pull'.

* gnus-demon.el (gnus-demon-remove-handler): Use it.

* gnus-demon.el (gnus-demon-remove-handler): Use it.

* gnus-group.el (gnus-group-make-web-group): Use it.

* gnus-msg.el (gnus-setup-message): Use it.

* gnus-sum.el (gnus-mark-article-as-unread)
(gnus-summary-mark-article-as-unread, gnus-summary-remove-bookmark)
(gnus-summary-set-bookmark): Use it.

* gnus-util.el (gnus-alist-pull): Rename `gnus-pull'.

* gnus.el (gnus-group-remove-parameter): Use it.