DEP: Deprecate that comparisons ignore errors.

This means that for example broadcasting errors get raised.

The array_equiv function is changed to explicitely test
if broadcasting is possible. It may be nice to do this
test differently, but I am not sure if that is possible.

Create a FutureWarning for comparisons to None, which
should result in areal elementwise (object) comparisons.

Slightly adepted a wrong test.

Poly changes: Some changes in the polycode was necessary,
the one is probably a bug fix, the other needs to be
thought over, since len check is not perfect maybe, since
it is more liekly to raise raise an error.