[MLton] MLTON_THREAD

[Stephen Weeks]

Making the unadorned operation for preparing threads be 

	val prepare: unit t -> Ready.t

is somewhat at odds with the polymorphic type constructor

	type 'a t

With the type constructor as it stands, I would expect the unadorned
operation to make use of the polymorphism, and the monomorphic
special-case to be adorned.  I won't go so far as to say that this is
one of our conventions, but it's close, and I think it does add weight
to making the unadorned prepare function be one of the following

	val prepare: 'a t * 'a -> Ready.t
	val prepare: 'a t * (unit -> 'a) -> Ready.t

Food for thought.

In any case, once this is settled (if it isn't already :-), we should
patch the thread regressions.