all DBs now support ON UPDATE CASCADE other than Oracle, there's no need
to try to reimplement more functionality here and users should be encouraged
to forego natural PKs unless their target platform supports them.
references #2666

mapper_configured(), after_configured(), and before_configured().

by mock and other __getattr__ impostors

- Fixes to the ORM and to the postgresql JSON type regarding the
``None`` constant in conjunction with the Postgresql :class:`.JSON` type.  When
the :paramref:`.JSON.none_as_null` flag is left at its default
value of ``False``, the ORM will now correctly insert the Json
"'null'" string into the column whenever the value on the ORM
object is set to the value ``None`` or when the value ``None``
is used with :meth:`.Session.bulk_insert_mappings`,
**including** if the column has a default or server default on it.  This
makes use of a new type-level flag "evaluates_none" which is implemented
by the JSON type based on the none_as_null flag. fixes #3514
- Added a new constant :attr:`.postgresql.JSON.NULL`, indicating
that the JSON NULL value should be used for a value
regardless of other settings. part of fixes #3514

- The "hashable" flag on special datatypes such as :class:`.postgresql.ARRAY`,
:class:`.postgresql.JSON` and :class:`.postgresql.HSTORE` is now
set to False, which allows these types to be fetchable in ORM
queries that include entities within the row.  fixes #3499
- The Postgresql :class:`.postgresql.ARRAY` type now supports multidimensional
indexed access, e.g. expressions such as ``somecol[5][6]`` without
any need for explicit casts or type coercions, provided
that the :paramref:`.postgresql.ARRAY.dimensions` parameter is set to the
desired number of dimensions. fixes #3487
- The return type for the :class:`.postgresql.JSON` and :class:`.postgresql.JSONB`
when using indexed access has been fixed to work like Postgresql itself,
and returns an expression that itself is of type :class:`.postgresql.JSON`
or :class:`.postgresql.JSONB`.  Previously, the accessor would return
:class:`.NullType` which disallowed subsequent JSON-like operators to be
used. part of fixes #3503
- The :class:`.postgresql.JSON`, :class:`.postgresql.JSONB` and
:class:`.postgresql.HSTORE` datatypes now allow full control over the
return type from an indexed textual access operation, either ``column[someindex].astext``
for a JSON type or ``column[someindex]`` for an HSTORE type,
via the :paramref:`.postgresql.JSON.astext_type` and
:paramref:`.postgresql.HSTORE.text_type` parameters. also part of fixes #3503
- The :attr:`.postgresql.JSON.Comparator.astext` modifier no longer
calls upon :meth:`.ColumnElement.cast` implicitly, as PG's JSON/JSONB
types allow cross-casting between each other as well.  Code that
makes use of :meth:`.ColumnElement.cast` on JSON indexed access,
e.g. ``col[someindex].cast(Integer)``, will need to be changed
to call :attr:`.postgresql.JSON.Comparator.astext` explicitly.  This is
part of the refactor in references #3503 for consistency in operator
use.

- ensure that kwargs can be modified in-place within InstanceEvents.init
and that these take effect for the __init__ method.
- improve documentation for these and related events, including
that kwargs can be modified in-place.

to function for a many-to-one relationship.  The loader used an
API to place "None" into the dictionary which no longer actually
writes a value; this is a side effect of :ticket:`3061`.
- remove InstanceState._initialize() totally, it's used nowhere
else and no longer does what it says it does
- fill in fowards-port version ids throughout the changes for 1.0.9

didn't implement ``__slots__``, and therefore meant all subclasses
of that class didn't either, negating the rationale for ``__slots__``
to be in use.  Didn't cause any issue except on IronPython
which apparently does not implement ``__slots__`` behavior compatibly
with cPython.
Fixes #3494