Schema update generates "Possibly failed to update database schema"

When running "./cake database" to update an existing database schema, "Possibly failed to update database schema" is generated. This is because ParseSchema (called in DatabaseShell::main) is generating bad SQL for Postgres.

eg: ALTER TABLE cm_cos ALTER COLUMN id SERIAL
which (1) should be ALTER TABLE cm_cos ALTER COLUMN id TYPE SERIAL
and (2) SERIAL isn't usable in an ALTER TABLE statement