There is another field I missed, index_interval. It is not actually used for
2.1.8 - so that's why it is easy to stop, but it at least exists.
2.1.8 already has "min_index_interval" and "max_index_interval". If we see a
table that contains index_interval, that will become "min_index_interval".
Signed-off-by: Glauber Costa <glommer@cloudius-systems.com>