Use concord.h.

Use concord.h.
(CHISE_DS_Type): Use `enum CONCORD_Backend_Type' instead of `enum
CHISE_DS_Type'.
(CHISE_DS_Berkeley_DB): New macro to wrap
`CONCORD_Backend_Berkeley_DB'.
(CHISE_DS): Use `CONCORD_Genre_Table' instead of `struct CHISE_DS'.
(CHISE_Value): Use `CONCORD_String_Tank' instead of `DBT'.
(chise_value_size): Changed to non-inline function.
(chise_value_data): Likewise.
(chise_value_to_c_string): Likewise.
(struct CHISE_Feature_Table): Abolished.
(CHISE_Feature): Use `CONCORD_Feature' instead of
`CHISE_Feature_Table*'.
(struct CHISE_CCS_Table): Abolished.
(CHISE_CCS): Use `CONCORD_INDEX' instead of `CHISE_CCS_Table*'.
(struct CHISE_Property_Table): Abolished.
(CHISE_Property): Use `CONCORD_Feature' instead of
`CHISE_Property_Table*'.