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

[Stephen Weeks]

What do people think about making -detect-overflow and -safe expert
options?  I haven't seen them used to good effect in a long, long
time.  Their default is sensible (i.e. respect the semantics), so I
don't think ordinary users need them.  The motivation for switching
them from normal to expert is to keep the list of normal options as
small as possible.

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.