(decode-char): Refer to the translation

(decode-char): Refer to the translation
hash table named utf-subst-table-for-decode.  Refer to the
translation table utf-translation-table-for-decode instead of
utf-8-translation-table-for-decode.
(encode-char): Refer to the translation hash table named
utf-subst-table-for-encode.  Refer to the translation table
utf-translation-table-for-encode instead of
utf-8-translation-table-for-encode.