[Python-3000] longobject.c and Windows x64

[Trent Nelson]

> On Windows x64, sizeof(size_t) > sizeof(long), so the
> existing PyLong_FromSsize_t and PyLong_FromSize_t
> implementations in longobject.c are just plain wrong.

There are a whole bunch of other areas where longobject.c could do with casts to silence Windows x64 compiler warnings (where it's safe to cast), and a few areas where we're going to be losing bits where we shouldn't be (i.e. long_getN() calling PyLong_FromLong() against Py_intptr_t).  Should I just go through and commit fixes where I find issues, or would people prefer something in tracker or discussion on the list beforehand?

        Trent.