"auto" now so True can indicate the dialect would support this

"auto increment" column has been changed, such that autoincrement
is no longer implicitly enabled for a :class:`.Table` that has a
composite primary key.  In order to accommodate being able to enable
autoincrement for a composite PK member column while at the same time
maintaining SQLAlchemy's long standing behavior of enabling
implicit autoincrement for a single integer primary key, a third
state has been added to the :paramref:`.Column.autoincrement` parameter
``"auto"``, which is now the default. fixes #3216
- The MySQL dialect no longer generates an extra "KEY" directive when
generating CREATE TABLE DDL for a table using InnoDB with a
composite primary key with AUTO_INCREMENT on a column that isn't the
first column;  to overcome InnoDB's limitation here, the PRIMARY KEY
constraint is now generated with the AUTO_INCREMENT column placed
first in the list of columns.

convention would not properly work with pickle.  The attribute was
skipped leading to inconsistencies and failures if the unpickled
:class:`.MetaData` object were used to base additional tables
from.
fixes #3362

conventions that include the token ``%(column_0_name)s``; the
constraint expression is scanned for columns.  Additionally,
naming conventions for check constraints that don't include the
``%(constraint_name)s`` token will now work for :class:`.SchemaType`-
generated constraints, such as those of :class:`.Boolean` and
:class:`.Enum`; this stopped working in 0.9.7 due to :ticket:`3067`.
fixes #3299

the logic used to link a :class:`.ForeignKey` to its parent could fail
when the foreign key used "link_to_name=True" in conjunction with
a target :class:`.Table` that would not receive its parent column until
later, such as within a reflection + "useexisting" scenario,
if the target column in fact had a key value different from its name,
as would occur in reflection if column reflect events were used to
alter the .key of reflected :class:`.Column` objects so that the
link_to_name becomes significant.  Also repaired support for column
type via FK transmission in a similar way when target columns had a
different key and were referenced using link_to_name.
fixes #3298

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