(ispell-word): More fboundp checks.

(ispell-word): More fboundp checks.

(ispell-find-aspell-dictionaries): New command.
(ispell-have-aspell-dictionaries): New variable.
(ispell-aspell-data-dir, ispell-aspell-dict-dir): New variables.
(ispell-get-aspell-config-value): New function.
(ispell-aspell-find-dictionary): New function.
(ispell-aspell-add-aliases): New function.
(ispell-valid-dictionary-list): Call ispell-find-aspell-dictionaries if
appropriate.  Don't look for ispell dictionaries if we use aspell.
(ispell-menu-map): Don't build a submenu of dictionaries.