for an insert from select are the string names, and not
the Column objects.  The MSSQL dialect in particular relies upon
checking for these keys in params to know if identity insert
should be on.  references #3360

That is, after exhausing all rows using the fetch methods, the
DBAPI cursor is released as before and the object may be safely
discarded, but the fetch methods may continue to be called for which
they will return an end-of-result object (None for fetchone, empty list
for fetchmany and fetchall).   Only if :meth:`.ResultProxy.close`
is called explicitly will these methods raise the "result is closed"
error.
fixes #3330 fixes #3329

such that they are matched to the received result set positionally,
rather than by name.  Originally, this was seen as a way to handle
cases where we had columns returned with difficult-to-predict names,
though in modern use that issue has been overcome by anonymous
labeling.   In this version, the approach basically reduces function
call count per-result by a few dozen calls, or more for larger
sets of result columns.  The approach still degrades into a modern
version of the old approach if textual elements modify the result
map, or if any discrepancy in size exists between
the compiled set of columns versus what was received, so there's no
issue for partially or fully textual compilation scenarios where these
lists might not line up.  fixes #918
- callcounts still need to be adjusted down for this so zoomark
tests won't pass at the moment

and parameters are not displayed if None, reducing confusion for
error messages that weren't related to a statement.  The full
module and classname for the DBAPI-level exception is displayed,
making it clear that this is a wrapped DBAPI exception.  The
statement and parameters themselves are bounded within a bracketed
sections to better isolate them from the error message and from
each other.
fixes #3172

the  python 3 merge, now does not expect percent signs (e.g.
as used as the modulus operator and others) to be doubled,
even when using the "pyformat" bound parameter format (this
change is not documented by Mysqlconnector).  The dialect now
checks for py2k and for mysqlconnector less than version 2.0
when detecting if the modulus operator should be rendered as
``%%`` or ``%``.
- Unicode SQL is now passed for MySQLconnector version 2.0 and above;
for Py2k and MySQL < 2.0, strings are encoded.  Note that mysqlconnector
as of 2.0.1 appears to have a bug with unicode DDL on py2k, so the tests here
are skipping until we observe it's fixed.
- take out profiling on mysqlconnector, callcounts vary too much with
its current development speed

constructs are now importable from the "from sqlalchemy" namespace,
just like every other Core construct.
- The implicit conversion of strings to :func:`.text` constructs
when passed to most builder methods of :func:`.select` as
well as :class:`.Query` now emits a warning with just the
plain string sent.   The textual conversion still proceeds normally,
however.  The only method that accepts a string without a warning
are the "label reference" methods like order_by(), group_by();
these functions will now at compile time attempt to resolve a single
string argument to a column or label expression present in the
selectable; if none is located, the expression still renders, but
you get the warning again. The rationale here is that the implicit
conversion from string to text is more unexpected than not these days,
and it is better that the user send more direction to the Core / ORM
when passing a raw string as to what direction should be taken.
Core/ORM tutorials have been updated to go more in depth as to how text
is handled.
fixes #2992

on :class:`.Insert`.  This helps to fix a bug where an
INSERT...FROM SELECT construct would inadvertently be compiled
as "implicit returning" on supporting backends, which would
cause breakage in the case of an INSERT that inserts zero rows
(as implicit returning expects a row), as well as arbitrary
return data in the case of an INSERT that inserts multiple
rows (e.g. only the first row of many).
A similar change is also applied to an INSERT..VALUES
with multiple parameter sets; implicit RETURNING will no longer emit
for this statement either.  As both of these constructs deal
with varible numbers of rows, the
:attr:`.ResultProxy.inserted_primary_key` accessor does not
apply.   Previously, there was a documentation note that one
may prefer ``inline=True`` with INSERT..FROM SELECT as some databases
don't support returning and therefore can't do "implicit" returning,
but there's no reason an INSERT...FROM SELECT needs implicit returning
in any case.   Regular explicit :meth:`.Insert.returning` should
be used to return variable numbers of result rows if inserted
data is needed.
fixes #3169