Casting errors interrupt Iteration
----------------------------------
NumPy sometimes has issues reporting errors during casting
correctly. This is rare, since the vast majority of casts
will never result in errors.
However, in some cases of casting errors less of the result
may be written back. The state of arrays involved in errors
should *always* be considered undefined.
Possible changes occur for:

* Universal functions when casting is unsafe (rare)
* Advanced index assignments
* The lowlevel `numpy.nditer` API.

For users of the ``NpyIter`` C-API such cast errors will now
cause the `iternext()` function to return 0 and thus abort
iteration.
Currently, there is no API to detect such an error directly.
It is necessary to check ``PyErr_Occurred()``, which
may be problematic in combination with ``NpyIter_Reset``.
These issues always existed, but new API could be added
if required by users.


Add release note for casting error changes
DOC: Add release note for casting error changes
