ha_innobase::prepare_inplace_alter_table(): Unless the table is
being rebuilt, determine the maximum column length based on the
current ROW_FORMAT of the table. When TABLE_SHARE (and the .frm file)
contains no explicit ROW_FORMAT, InnoDB table creation or rebuild
will use innodb_default_row_format.

Based on mysql/mysql-server@3287d33acdc4260806a2a407ca15e9d1e04dddcb