the creation of strong references within the Session;
an object will no longer have an internal reference cycle
created if it's in the transient state or moves into the
detached state - the strong ref is created only when the
object is attached to a Session and is removed when the
object is detached.  This makes it somewhat safer for an
object to have a `__del__()` method, even though this is
not recommended, as relationships with backrefs produce
cycles too.  A warning has been added when a class with
a `__del__()` method is mapped.
[ticket:2708]

query when refreshing an inheritance-mapped class
where the superclass was mapped to a non-Table
object, like a custom join() or a select(),
running a query that assumed a hierarchy that's
mapped to individual Table-per-class.
[ticket:2697]

  subclass could insert the row for the "sub" table
  before the parent table, if the two tables had no
  ForeignKey constraints set up between them.
  Also in 0.7.11. [ticket:2689]
- fix a glitch in the assertsql.CompiledSQL fixture regarding
when a multiparam compiledSQL is used within an AllOf
- add a new utility function randomize_unitofwork() which
does the function of --reversetop

- other cleanup
- don't need compat.decimal, that approach never panned out. hopefully
outside libs aren't pulling it in, they shouldn't be

mapper configuration; will now test for name conflicts on
superclasses and subclasses, in addition to the current mapper,
as these conflicts break things just as much.  This is new for
0.8, but see below for a warning that will also be triggered
in 0.7.11.
- Improved the error message emitted when a "backref loop" is detected,
that is when an attribute event triggers a bidirectional
assignment between two other attributes with no end.
This condition can occur not just when an object of the wrong
type is assigned, but also when an attribute is mis-configured
to backref into an existing backref pair.  Also in 0.7.11.
- A warning is emitted when a MapperProperty is assigned to a mapper
that replaces an existing property, if the properties in question
aren't plain column-based properties.   Replacement of relationship
properties is rarely (ever?) what is intended and usually refers to a
mapper mis-configuration.   Also in 0.7.11.
[ticket:2674]

an "orphan" has been modified to more closely match the
behavior as that of persistent objects, which is that the object
is expunged from the :class:`.Session` as soon as it is
de-associated from any of its orphan-enabled parents.  Previously,
the pending object would be expunged only if de-associated
from all of its orphan-enabled parents.  The new flag ``legacy_is_orphan``
is added to :func:`.orm.mapper` which re-establishes the
legacy behavior. [ticket:2655]

associated with the ORM or its extensions can be retrieved.
This fulfills the common request of being able to inspect
all :class:`.QueryableAttribute` descriptors in addition to
extension types such as :class:`.hybrid_property` and
:class:`.AssociationProxy`.  See :attr:`.Mapper.all_orm_descriptors`.

- paths now store Mapper + MapperProperty now instead of string key,
so that the parent mapper for the property is known, supports same-named
properties on multiple subclasses
- the Mapper within the path is now always relevant to the property
to the right of it.  PathRegistry does the translation now, instead
of having all the outside users of PathRegistry worry about it,
to produce a path that is much more consistent.  Paths are now
consistent with mappings in all cases.  Special logic to get at
"with_polymorphic" structures and such added also.
- AliasedClass now has two modes, "use_mapper_path" and regular;
"use_mapper_path" is for all those situations where we put an AliasedClass
in for a plain class internally, and want it to "path" with the
plain mapper.
- The AliasedInsp is now the first class "entity" for an AliasedClass,
and is passed around internally and used as attr._parententity
and such.  it is the AliasedClass analogue for Mapper.