This fixes all known issues when connecting to discourse over IPv6.
This table has no primary key, so the migration is done with update_all,
for each ip address in the views table. Since this table can potentially
grow quite large, this process might take a long time. I don't know any
way around this, though.
This migration uses a SQL command to populate the new field from the old
one, so as not to rely on the View model class, which should keep the
migration from failing if that class is modified in the future.
