Added empty_ok and used it for sindex_range_t fields.
Made the on-disk format be serialized datum_t instead of serialized cJSON.
Made rdb_modification_info_t::deleted and added be datum_t instead of cJSON.
Made transform_apply use datum_t.
Removed unused rdb_modification_report_cb_t methods add_row, delete_row, and replace_row.
Made rget_read_response_t::data be a datum_t.