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

with Firebird, so that the values are again rendered inline when
this is selected.  Related to :ticket:`3034`.
fixes #3381

:ticket:`3184` would cause index operations to fail on Postgresql
versions 8.4 and earlier.  The enhancements are now
disabled when using an older version of Postgresql.
fixes #3343

using psycopg2 2.5.4 or greater, which features native conversion
of JSONB data so that SQLAlchemy's converters must be disabled;
additionally, the newly added psycopg2 extension
``extras.register_default_jsonb`` is used to establish a JSON
deserializer passed to the dialect via the ``json_deserializer``
argument.  Also repaired the Postgresql integration tests which
weren't actually round-tripping the JSONB type as opposed to the
JSON type.  Pull request courtesy Mateusz Susik.

- Repaired the use of the "array_oid" flag when registering the
HSTORE type with older psycopg2 versions < 2.4.3, which does not
support this flag, as well as use of the native json serializer
hook "register_default_json" with user-defined ``json_deserializer``
on psycopg2 versions < 2.5, which does not include native json.

consists mainly of adjusting fixtures to ensure connections are closed
explicitly.  psycopg2cffi also handles unicode bind parameter
names differently than psycopg2, and seems to possibly have a little less
control over floating point values at least in one test which is
marked as a "fail", though will see if it runs differently on linux
than osx..
- changelog for psycopg2cffi, fixes #3052

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