it to prevent excess memory usage with yield_per

objects that made use of the ``__clause_element__()`` method and
returned an object that was an ORM-mapped
:class:`.InstrumentedAttribute` and not explicitly a
:class:`.ColumnElement` would fail to be correctly
handled when passed as an expression to :meth:`.Session.query`.
The logic in 0.9 happened to succeed on this, so this use case is now
supported. fixes #3448

object would fail to accommodate the labeled SQL expression
in all cases, such that any SQL operation that made use of
:meth:`.Label.self_group` would use the original unadapted
expression.  One effect of this would be that an ORM :func:`.aliased`
construct would not fully accommodate attributes mapped by
:obj:`.column_property`, such that the un-aliased table could
leak out when the property were used in some kinds of SQL
comparisons.
fixes #3445

that a Python descriptor is no longer used; repairs inspectability
of these methods including support for Sphinx documentation.

Called after the :meth:`.Engine.dispose` method is called.

psycopg2cffi dialect, in particular that the current 2.7.0 version
does not have native support for the JSONB type.  The version detection
for psycopg2 features has been tuned into a specific sub-version
for psycopg2cffi.  Additionally, test coverage has been enabled
for the full series of psycopg2 features under psycopg2cffi.
fixes #3439

- alter the approach so that the initial callable is working just like add_criteria/with_criteria