Add Type_handler::KEY_pack_flags()

       /* Use packed keys for long strings on the first column */

       if (!((*db_options) & HA_OPTION_NO_PACK_KEYS) &&

           !((create_info->table_options & HA_OPTION_NO_PACK_KEYS)) &&

           (key_part_length >= KEY_DEFAULT_PACK_LENGTH &&

            (sql_field->real_field_type() == MYSQL_TYPE_STRING ||

             sql_field->real_field_type() == MYSQL_TYPE_VARCHAR ||

             f_is_blob(sql_field->pack_flag))) && !is_hash_field_needed)

       {

         if ((column_nr == 0 && f_is_blob(sql_field->pack_flag)) ||

             sql_field->real_field_type() == MYSQL_TYPE_VARCHAR)

           key_info->flags|= HA_BINARY_PACK_KEY | HA_VAR_LENGTH_KEY;

         else

           key_info->flags|= HA_PACK_KEY;

       }

virtual ulong KEY_pack_flags(uint column_nr) const { return 0; }

       /* Use packed keys for long strings on the first column */

       if (!((*db_options) & HA_OPTION_NO_PACK_KEYS) &&

           !((create_info->table_options & HA_OPTION_NO_PACK_KEYS)) &&

           (key_part_length >= KEY_DEFAULT_PACK_LENGTH) &&

           !is_hash_field_needed)

       {

         key_info->flags|= sql_field->type_handler()->KEY_pack_flags(column_nr);

       }