- bindparam() gets a new option "callable", which is a lambda or def

- bindparam() gets a new option "callable", which is a lambda or def
evaluated at execution time to determine the value.  This replaces
the implicit recognition of callables sent as the primary value
of bindparam(), which was an undocumented behavior used by the ORM.
The argument is separated now so that values can be passed to
bindparams that are also callables without ambiguity, such
as user defined objects that include a __call__() method.
[ticket:1950]