Remove Emacs 21 stuff.

Remove Emacs 21 stuff.

gmm-utils.el (gmm-tool-bar-from-list): Always use tool-bar-local-item and tool-bar-local-item-from-menu.
gnus-agent.el (gnus-agent-make-mode-line-string): Always use mode-line-highlight face for Emacs.
gnus-art.el (toplevel): Don't bind recursive-load-depth-limit while loading gnus-sum.elc; don't autoload canlock-verify.
gnus-art.el (gnus-article-jump-to-part): Use read-number.
gnus-art.el (gnus-insert-mime-button, gnus-insert-mime-security-button): Remove Emacs pre-21 compatible code for help-echo.
gnus-art.el (gnus-article-next-page-1): No need to adjust the number of lines.
gnus-art.el (gnus-article-describe-bindings): Always use help-buffer.
gnus-audio.el (gnus-audio-inline-sound): Comment fix.
gnus-cus.el (gnus-custom-mode): Comment fix.
gnus-group.el (gnus-group-update-tool-bar): Comment fix.
gnus-sum.el (gnus-remove-overlays): Doc fix.
gnus-util.el (gnus-select-frame-set-input-focus): Remove Emacs 21 compatible code.