(get-language-info): Accept a symbol

(get-language-info): Accept a symbol
as the arg LANGUAGE-NAME.
(set-language-info): Likewise.
(set-language-info-alist): Likewise.
(register-input-method): Accept a symbol as the args INPUT-METHOD
and LANGUAGE-NAME.
(activate-input-method): Accept a symbol as the args INPUT-METHOD.
(describe-input-method): Likewise.
(read-multilingual-string): Likewise.
(set-language-environment): Accept a symbol as the arg
LANGUAGE-NAME.
(describe-language-environment): Likewise.