Merge changes made in Gnus master; Remove dead code

Merge changes made in Gnus master; Remove dead code

* mail-source.el (mail-source-movemail-and-remove): Remove, unused.
* nntp.el (nntp-send-nosy-authinfo, nntp-send-authinfo-from-file)
  (nntp-async-timer-handler): Remove, unused.
* nnimap.el (nnimap-get-responses): Remove, unused.
* nnheader.el (mail-header-set-extra): Remove, unused.
* netrc.el (netrc-find-service-number, netrc-store-data): Remove,
  unused.
* mm-view.el (mm-view-sound-file): Remove, unused.
* mm-url.el (mm-url-fetch-simple, mm-url-fetch-form)
  (mm-url-encode-multipart-form-data): Remove, unused.
* message.el (message-remove-signature, message-make-host-name)
  (message-fill-address): Remove, unused.
* gnus.el (gnus-writable-groups, gnus-group-guess-prefixed-name)
  (gnus-group-guess-full-name, gnus-group-guess-prefixed-name): Remove,
  unused.
* gnus-uu.el (gnus-uu-find-name-in-shar): Remove, unused.
* gnus-util.el (gnus-extract-address-component-name)
  (gnus-extract-address-component-email, gnus-sortable-date)
  (gnus-alist-to-hashtable, gnus-hashtable-to-alist)
  (gnus-process-live-p): Remove, unused.
* gnus-topic.el (gnus-group-parent-topic): Remove, unused.
* gnus-sum.el (gnus-score-set-default, gnus-article-parent-p)
  (gnus-article-read-p, gnus-uncompress-marks): Remove, unused.
  (gnus-summary-set-current-mark): Remove obsolete, empty and unused
  function.
* gnus-start.el (gnus-kill-newsgroup): Remove unused obsolete function.
* gnus-score.el (gnus-summary-score-crossposting)
  (gnus-score-regexp-bad-p): Remove, unused.
* gnus-salt.el (gnus-tree-goto-article): Remove, unused.
* gnus-range.el (gnus-sublist-p): Remove, unused.
* gnus-msg.el (gnus-mail-parse-comma-list, gnus-put-message): Remove,
  unused.
* gnus-kill.el (gnus-Newsgroup-kill-file): Remove, unused.
* gnus-int.el (gnus-list-active-group, gnus-request-group-articles)
  (gnus-request-associate-buffer): Remove, unused.
* gnus-group.el (gnus-group-set-method-info)
  (gnus-group-set-params-info): Remove, unused.
* gnus-fun.el (gnus-shell-command-to-string)
  (gnus-shell-command-on-region): Remove, unused.
* gnus-cite.el (gnus-cited-line-p): Remove, unused.
* gnus-art.el (gnus-article-text-type-exists-p)
  (article-translate-characters, gnus-article-hide-text-of-type)
  (gnus-kill-sticky-article-buffers, gnus-article-maybe-highlight):
  Remove, unused.