Incorrect implementation of numpy.copyto

[Micha Gorelick]

As it stands in 1f83790, numpy.copyto is simply a thin wrapper to ndarray.fill. However, both of these functions have drastically different uses. ndarray.fill fills an array with a scalar value while numpy.copyto copies one ndarray's data into another pre-allocated ndarray.

[mattip]

copyto() was improved on latest HEAD, it now passes numpy tests. Please reopen with an example if it fails to work as advertised