[Cython] Stealing/borrowed references semantics

[Stefan Behnel]

Dag Sverre Seljebotn wrote:
> it would be syntax candy for an extra incref. I can work around 
> this now by:
> 
> cdef extern void Real_PyList_SET_ITEM "PyList_SET_ITEM"(object, 
> Py_ssize_t, object)
> 
> cdef inline void PyList_SET_ITEM(object a, Py_ssize_t b, object c):
>      Py_INCREF(c)
>      Real_PyList_SET_ITEM(a, b, c)
> 
> For ~20 functions I am likely not going to bother; while simply declaring
> 
> cdef extern void PyList_SET_ITEM(object, Py_ssize_t, stolen object):

I'm fine with that, as long as we only allow it inside of argument lists
(preferrably only "extern" argument lists).

Stefan