Update numpy.i

1. Removed a few unnecessary data_temp = NULL; declarations -- 2. Cleaned-up my use of either PyCObject_FromVoidPtr or
PyArray_BASE. Both are now deprecated (this to be scrutinised!). -- 3. Cleaned-up various warnings, in particular
relating to the use of  SWIG_Python_AppendOutput($result, XXX) where
XXX should be a PyObject but was a PyArrayObject.