; Improve doc strings of Speedbar

; Improve doc strings of Speedbar

* lisp/speedbar.el (speedbar-extension-list-to-regex)
(speedbar-query-confirmation-method)
(speedbar-show-unknown-files, speedbar-use-imenu-flag)
(speedbar-track-mouse-flag, speedbar-default-position)
(speedbar-sort-tags, speedbar-directory-button-trim-method)
(speedbar-smart-directory-expand-flag)
(speedbar-hide-button-brackets-flag, speedbar-vc-do-check)
(speedbar-vc-indicator, speedbar-obj-do-check)
(speedbar-frame-mode, speedbar-handle-delete-frame)
(speedbar-show-info-under-mouse, speedbar-item-info)
(speedbar-item-rename, speedbar-item-delete)
(speedbar-initial-keymap, speedbar-insert-files-at-point)
(speedbar-generic-list-positioned-group-p)
(speedbar-generic-list-tag-p, speedbar-check-read-only)
(speedbar-tag-file, speedbar-tag-expand)
(speedbar-find-file-in-frame, speedbar-parse-tex-string)
(speedbar-buffer-click): Doc fixes.

(cherry picked from commit 01bcc6961a6b0db36c371c9016d6eb00a1ae8ea2)