the indexing.  this is for more natural operation.
- also add cast() to the JSON expression to complement astext. This integrates
the CAST call which will be needed frequently.  Part of [ticket:2687].
- it's a little unclear how more advanced unicode attribute-access is going to go,
some quick attempts at testing yielded strange error messages from psycopg2.
- do other cross linking as mentioned in [ticket:2687].

yet the column is not the "auto increment" column, either because
it has a foreign key constraint or ``autoincrement=False`` set,
would attempt to fire the Sequence on INSERT for backends that don't
support sequences, when presented with an INSERT missing the primary
key value.  This would take place on non-sequence backends like
SQLite, MySQL. [ticket:2896]

of the given names would not be taken into account when generating
the INSERT statement, thus producing a mismatch versus the column
names in the given SELECT statement.  Also noted that
:meth:`.Insert.from_select` implies that Python-side insert defaults
cannot be used, since the statement has no VALUES clause. [ticket:2895]

``__repr__()``, particularly with regards to the MySQL integer/numeric/
character types which feature a wide variety of keyword arguments.
The ``__repr__()`` is important for use with Alembic autogenerate
for when Python code is rendered in a migration script.
[ticket:2893]

will now apply the given type to the given literal value on the
bind parameter side according
to the type given to the cast.   This essentially replaces what would
normally be the detected type of the literal value.   This only
takes effect if the auto-detected type of the literal value is either
"nulltype" (e.g. couldn't detect)
or a type that is of the same "affinity" as the cast type.
The net change here is that the :func:`.cast` function includes more
of the functionality already present in the :func:`.type_coerce` function.

- add support for "standalone" JSON objects; this involves getting CAST
to upgrade the given type of a bound parameter.  should add a core-only test
for this.
- add tests for "standalone" json round trips both with and without unicode
- add mechanism by which we remove psycopg2's "json" handler in order to get
the effect of using our non-native result handlers

backwards compatibility.  A note about backslashing escapes is added.
Because the Text() construct now supports bind params better, the example
given in the code raises an exception now, so that should cover us.
The exception itself has been enhanced to include the key name of the
bound param.  We're backporting this to 0.8 but 0.8 doesn't have the
text->bind behavior that raises.

doing the isinstance() check - currently used only by psycopg2 + native enum + py2k.
- didn't realize psycopg2 had UNICODEARRAY extension all this time; replace _PGArray
with just using UNICODEARRAY instead.
- replace unnecessary/inconsistent __import__ in _isolation_lookup.