Added commentary about stealthy functions.

Added commentary about stealthy functions.
(speedbar-message) new function.
(speedbar-y-or-n-p): New function
(speedbar-with-attached-buffer) Moved macro before reference.
Now uses `save-selected-window'.
(speedbar-mouse-hscroll, speedbar-track-mouse, speedbar-refresh,
speedbar-generic-item-info, speedbar-item-info-file-helper,
speedbar-item-delete, speedbar-insert-generic-list,
speedbar-timer-fn, speedbar-check-vc-this-line,
speedbar-check-obj-this-line, speedbar-fetch-dynaic-etags,
speedbar-buffers-item-info) Use speedbar-message.
(speedbar-item-info) Limit `message-log-max'.
(speedbar-item-load, speedbar-item-copy, speedbar-item-rename,
speedbar-item-delete, speedbar-item-object-delete,
speedbar-buffer-kill-buffer) Use speedbar-y-or-n-p.