bignums and native back end

[Matthew Fluet]

> > Is there any thing I can do to get bignums working with the native
back end?
>
> They already work (although maybe not with the release you have).

Right now, there is assembly for the following primitives:

IntInf_isSmall
IntInf_areSmall
IntInf_fromArray  \
IntInf_toVector    \
IntInf_fromWord    / all of these are just moves, but correspond to a
IntInf_toWord     /   type cast in CPS

IntInf_{op} are implemented as C function calls, but to the IntInf_do_{op}
functions in int-inf.c.

This corresponds to expanding out all of the #defines in int-inf.h and    
coding up their assembly equivalents.