(info-complete): Rewrite minibuffer completion code.

(info-complete): Rewrite minibuffer completion code.

(info-lookup-minor-mode, turn-on-info-lookup):
Added minor mode interface.
(info-lookup-minor-mode-string): New variable.
(info-lookup-minor-mode-map): New variable.

Provide a work-around if the custom library is not available.

(info-lookup-other-window-flag)
(info-lookup-highlight-face): Variables customized.

(info-lookup-alist): No longer customizable.
(info-lookup-add-help, info-lookup-maybe-add-help): Interface
functions for adding new modes.
(info-lookup-add-help*): New function.
(info-lookup-symbol-alist, info-lookup-file-alist): Variables deleted.
This info is specified now by calling info-lookup-maybe-add-help
and info-lookup-add-help.