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

isn't appended to the list.  reflection makes use of this.

when presented with duplicate columns.  The behavior of emitting a
warning and replacing the old column with the same name still
remains to some degree; the replacement in particular is to maintain
backwards compatibility.  However, the replaced column still remains
associated with the ``c`` collection now in a collection ``._all_columns``,
which is used by constructs such as aliases and unions, to deal with
the set of columns in ``c`` more towards what is actually in the
list of columns rather than the unique set of key names.  This helps
with situations where SELECT statements with same-named columns
are used in unions and such, so that the union can match the columns
up positionally and also there's some chance of :meth:`.FromClause.corresponding_column`
still being usable here (it can now return a column that is only
in selectable.c._all_columns and not otherwise named).
The new collection is underscored as we still need to decide where this
list might end up.   Theoretically it
would become the result of iter(selectable.c), however this would mean
that the length of the iteration would no longer match the length of
keys(), and that behavior needs to be checked out.
fixes #2974
- add a bunch more tests for ColumnCollection