this is dead code since on 4.2 we're loading oid.rb from AR's Postgre's support
[mysql] core adapter compat - missing initialize_schema_migrations_table and helpers
[mysql] make sure new_column works - we now export a MySQL::Column constant
[mysql] fix new_column and move Column#initialize + introduce a AR42 constant
[postgres] export Column class (simplifies code and aligns with a "future" convention)
export Column classes for MSSQL and Oracle