(Fsave_charset_mapping_table): Use `chise_ds_open_ccs_table',

(Fsave_charset_mapping_table): Use `chise_ds_open_ccs_table',
`chise_ccst_put_char' and `chise_ccst_close' instead of
`chise_ds_open_decoding_table', `chise_dt_put_char' and
`chise_dt_close'.
(load_char_decoding_entry_maybe): Use `chise_ds_open_ccs_table',
`chise_ccs_decode' and `chise_ccst_close' instead of
`chise_ds_open_decoding_table', `chise_dt_get_char' and
`chise_dt_close'.