[polyml] Int32 hack and patch to Word32.sml

Vesa Karvonen wrote:

Poly/ML does not currently seem to provide any fixed precision integer modules. Porting some of my code to Poly/ML would be easier if Poly/ML would provide a fixed precision integer module, like Int32, and the associated overloads. Having arbitrary precision integers as the default Int module is not a problem. Attached is a quick hack that implements Int32 for Poly/ML. I tested it briefly interactively and it seems to work. I also noticed that the negation operator, ~, has not been overloaded for Word32 and added the appropriate overload.

Thanks, I've added it. While checking it I noticed that Word32.~ wasn't actually right so I've fixed that as well.

David.