The total_*_size columns in maia_stats overflow too quickly

[rjl]

The total_*_size columns in maia_stats are set to INTEGER for PostgreSQL (2 GB limit) and UNSIGNED INTEGER for MySQL (4 GB limit), but the value being stored in these columns is cumulative, and will eventually overflow the data type's allocation. Since it is not unreasonable for a site that processes 200+ 5 MB items to exceed a 2 GB limit, this will clearly result in an overflow error eventually. A larger data type is needed for these columns.

[rjl]

Fixed in [1002], where the PostgreSQL schema now uses BIGINTs, and the MySQL schema uses UNSIGNED BIGINTs. These 8-byte integers should be large enough to contain many centuries of accumulated mail sizes.

[rjl]

Changesets [1003] and [1004] complete this fix by applying the same solution to the maia_stats_history table and by updating the upgrade scripts accordingly.