Is it be feasible to add arithmetic operations
to the ctypes integer types?  Since ctypes is now
in the core, it would seem better to enhance ctypes
than provide a new module.

I think this would be valuable for rapid prototyping
of an algorithm in Python before translating it into
C.  In particular, it might help with detecting some
common C code bugs involving undefined behaviour---for
example, overflow in signed-integer arithmetic.