[MLton] enabling control diagnostics

[Stephen Weeks]

> Is it possible to enable diagnostics for a particular file? I am
> looking to print out the layouts in ssa/flatten.fun. If not how do
> you enable the control diagnostics to print out the layouts for ssa? 
> Is there a command line parameter I can pass or do I have to edit
> control.sml?

This can all be done on the command line

-diag-pass flatten
	will save the diagnostic output during the flatten pass

-keep-pass flatten
	will save the ssa before and after the flatten pass

-keep dot
	will save control flow graphs (as dot files) for each ssa function