[postgres] bit types are not longer reported as :string column types by AR 4.2
PostgreSQLAdapter::OID source from recent 4.1.x

https://github.com/rails/rails/blob/4-1-stable/activerecord/lib/active_record/connection_adapters/postgresql/oid.rb

latest commit https://github.com/rails/rails/commit/5e09ea06a640c0205f4c7db1
[postgres] OIDTypes helper that as compatible with AR 4.2