Fused types for 32 and 64bit systems

[fgregg]

@wolfgang-noichl, I think you want to used fused types to support both 32 and 64 bit systems. If you get that working, I'll merge it into master.

[wolfgang-noichl]

Fused types alone don't really work for that, since one cannot check the interior type (i.e. type(x) is float for x of fused type). I'd need another type-checking wrapper in front of all cython stuff...

For now, I'll just maintain my vanilla-32bit branch and try to keep it synced to upstream.