to start up listener collections; this pulls the overhead off of construction
and makes performance much like the descriptor version, while still allowing
slots.   Fix up some profiles.

allowing us to move to __slots__

as that of :ticket:`3199`, when the ``named=True`` parameter
would be used.  Some events would fail to register, and others
would not invoke the event arguments correctly, generally in the
case of when an event was "wrapped" for adaption in some other way.
The "named" mechanics have been rearranged to not interfere with
the argument signature expected by internal wrapper functions.
fixes #3197

ORM events but also engine events, where the usual logic of
"de duplicating" a redundant call to :func:`.event.listen`
with the same arguments would fail, for those events where the
listener function is wrapped.  An assertion would be hit within
registry.py.  This assertion has now been integrated into the
deduplication check, with the added bonus of a simpler means
of checking deduplication across the board.
fixes #3199

is being run itself, either from inside the listener or from a
concurrent thread, now raises a RuntimeError, as the collection used is
now an instance of ``colletions.deque()`` and does not support changes
while being iterated.  Previously, a plain Python list was used where
removal from inside the event itself would produce silent failures.
fixes #3163

and :func:`.event.listens_for`.  This is a convenience feature which
will wrap the given listener such that it is only invoked once.

level (e.g. on the :class:`.Mapper` or :class:`.ClassManager`
level, as opposed to on an individual mapped class, and also on
:class:`.Connection`) that also made use of internal argument conversion
(which is most within those categories) would fail to be removable.
fixes #2973

system would cause a recursion overflow due to usage of inspect.getargspec()
on it in order to detect a legacy calling signature for certain events,
and apparently there's no way to do this with a partial object.  Instead
we skip the legacy check and assume the modern style; the check itself
now only occurs for the SessionEvents.after_bulk_update and
SessionEvents.after_bulk_delete events.  Those two events will require
the new signature style if assigned to a "partial" event listener.
[ticket:2905]

into account the id() of the function itself and self, [ticket:2832]