[MLton] Continuations and MLton.Vector.create

[Andreas Rossberg]

I've always been sceptical of call/cc. IMO it is a dangerous operation. 
I consider it in the same class as a generic clone operator for copying 
arbritrary (stateful) data structures. Such an operation is well-known 
to break stateful abstraction, and hence is usually banned from 
languages that care about abstraction, because there is no way to 
protect against it.

In a somewhat similar way, call/cc allows copying control flow. This can 
break all stateful abstractions that provide higher-order operations. 
And there is no way to protect against that either.

I think that Vector.tabulate is just one instance of this more general 
problem. Much more dangerous scenarios are possible (just consider an 
iterator doing some locking).

   - Andreas