[MLton] making -detect-overflow and -safe expert options

[Matthew Fluet]

> What do people think about making -detect-overflow and -safe expert
> options?

Seems reasonable.  I've never needed them for anything.

> Similar thinking might apply to -ieee-fp and -inline.  But with
> -ieee-fp the default is to not respect the semantics.
> And -inline can
> have a major impact and seems to get used by ordinary users somewhat.

I think that John was going to put enough caveats in the spec to make
thinks o.k. on the x86. We'll see soone enough.

Maybe we need a second tier of options -- things that aren't likely to go
away (like all of the above), but which aren't really expert options.
I like the idea of having a very short normal options list.