what's given so we need to use a set() here.  contains_column is not within
any performance paths

need this collection except in the extend/update uses where we
create it ad-hoc.  simplifies pickling.  Compatibility with 1.0
should be OK as ColumnColleciton uses __getstate__ in any case
and the __setstate__ contract hasn't changed.
- Fixed bug in :class:`.Table` metadata construct which appeared
around the 0.9 series where adding columns to a :class:`.Table`
that was unpickled would fail to correctly establish the
:class:`.Column` within the 'c' collection, leading to issues in
areas such as ORM configuration.   This could impact use cases such
as ``extend_existing`` and others.  fixes #3632

for memoization on a class that uses slots.
- apply many more __slots__.  mem use for nova now at 46% savings

e.g. the ``func`` construct.  Previously, behavior for this method
was undefined.  The current behavior mimics that of pre-0.9.4,
which is that the function is turned into a single-column FROM
clause with the given alias name, where the column itself is
anonymously named.
fixes #3137

sqlalchemy/orm, sqlalchemy/event, sqlalchemy/testing

Python version < 2.6.5, working around the
"no unicode keyword arg" bug as these args are passed along as
keyword args within some reflection processes.
fixes #3123

to get all flake8 passing

specify a :func:`.text` expression as the target; the index no longer
needs to have a table-bound column present if the index is to be
manually added to the table, either via inline declaration or via
:meth:`.Table.append_constraint`. fixes #3028

adding an argument for a construct not previously included for any
special arguments would fail. fixes #3024