Integrate patch from Neal Norwitz. He writes:

Integrate patch from Neal Norwitz.  He writes:

"""
The attached patch fixes all the ctypes tests so they pass on amd64.
It also fixes several warnings.  I'm not sure what else to do with the
patch.  Let me know how you want to handle these in the future.

I'm not sure the patch is 100% correct.  You will need to decide what
can be 64 bits and what can't.  I believe
sq_{item,slice,ass_item,ass_slice} all need to use Py_ssize_t.  The
types in ctypes.h may not require all the changes I made.  I don't
know how you want to support older version, so I unconditionally
changed the types to Py_ssize_t.
"""

The patch is also in the ctypes SVN repository now, after small
changes to add compatibility with older Python versions.