[MLton] Signatures and def-use information

[Vesa Karvonen]

While browsing SML code, I'd like to be able to jump not just to the
definition of a binding, but also to the specification(s) of the
binding when such exist.  Also, being able to list all definitions of
a spec would also be nice.  It seems like def-use processing is done
after type-checking, so it should not be impossible to also keep
the relevant information for linking definitions to specifications.
I haven't yet looked at the code to figure out how to do this.
Helpful pointers are welcome. :)