profiling

[Stephen Weeks]

> The one, major, outstanding bug is that compiling -p a program without any
> references to MLton.Profile.* results in no profile information being
> gathered; we're being pimped by dead-code elimination, which eliminates
> all the side-effecting statements that start the profiling and install the
> atExit code. In fact, you need a reference to include a reference to
> MLton.Profile.{current,setCurrent}.  

I checked in a fix that only required changes to profile.sml.