See https://github.com/silverstripe/silverstripe-mssql/issues/14
for more info.
"bigint" doesn't work for PHP 32-bit, as the integer could get too big
for PHP to be able to interpret the value as an integer type. In that
case it would try to approximate it as a float, but that could lead
to a bad assumption for identity columns.
For compatibility, stick with standard "int" type which has a maximum
value of 2147483647.
Note that MySQLAdapter already has this maximum, so changing it to
this keeps this database adapter consistent with MySQL.
