[MLton] starting builds

[Stephen Weeks]

> Bug filed: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=327351

Great.  From the looks of the discussion it seems it will be fixed
soon.

In any case, I don't think it makes sense to rewrite MLton's
Real.{ceil,floor,round,trunc} to work around what is clearly a libc
bug.  It's not clear to me that on a platform where rint/festeround is
broken that floor is any more likely to work.  If I were implementing
libc I would do just as we did with MLton and implement floor in terms
of rint/festround when possible.