(chise_open_data_source): Interface change; allocate a CHISE_DS object

(chise_open_data_source): Interface change; allocate a CHISE_DS object
and return it.
(chise_ds_close): Renamed from `chise_close_data_source'; destroy the
specified CHISE_DS object.
(chise_ds_open_decoding_table): Renamed from
`chise_open_decoding_table' and changed the interface.
(chise_dt_close): Renamed from `chise_close_decoding_table'.
(chise_ds_open_feature_table): Renamed from `chise_open_feature_table'
and changed the interface.
(chise_ft_close): Renamed from `chise_close_feature_table'.
(chise_open_attribute_table): Interface change; allocate a
CHISE_Attribute_Table object and return it; require pointer for data
source object instead of db_dir.
(chise_close_attribute_table): Destroy the specified
CHISE_Attribute_Table object.