the delete function. (Question: should the attribute name also be
recorded in the getset object? That makes the protocol more work, but
may give us better error messages.)
- descrobject.c:descr_check(): only believe None means the same as
NULL if the type given is None's type.
- typeobject.c:wrap_descr_get(): don't "conventiently" default an
absent type to the type of the object argument. Let the called
function figure it out.