size of the many per-column objects we're hitting, but somehow the overall memory is
hardly being reduced at all in initial testing

- test_schema_2 is only on PG and doesn't need a drop all, omit this for now
- py3k has exception.args[0], not message

sort_tables_and_constraints function.
- The DDL generation system of :meth:`.MetaData.create_all`
and :meth:`.Metadata.drop_all` has been enhanced to in most
cases automatically handle the case of mutually dependent
foreign key constraints; the need for the
:paramref:`.ForeignKeyConstraint.use_alter` flag is greatly
reduced.  The system also works for constraints which aren't given
a name up front; only in the case of DROP is a name required for
at least one of the constraints involved in the cycle.
fixes #3282

to complement the :attr:`.Table.foreign_keys` collection,
as well as :attr:`.ForeignKeyConstraint.referred_table`.

- attempt to add a script to semi-automate the fixing of links

a type that was also a :class:`.TypeDecorator` would fail with
Python's "Cannot create a consistent method resolution order (MRO)"
error, when any kind of SQL comparison expression were used against
an object using this type.

VARBINARY(max) for large text/binary types.  The MSSQL dialect will
now respect this based on version detection, as well as the new
``deprecate_large_types`` flag.
fixes #3039