[MLton] MLton rules! (was: filedes = int)

[Stephen Weeks]

> It is indeed important that the interfacing to GMP is done right.
> 
> Calculations with numbers that bounce back and forth between the
> the fixnum and bignum size is likely to occur:
..
> Jaffer has some nice observations on where to direct the most
> attention to tuning the performance of arithemetical calculations.

FYI, MLton already has a pretty good interface to GMP.  We only use it
for bignum computations and do the fixnum-fixnum stuff on our own.