[developers] Finding the minimal type for which a feature is declared

[Emily M. Bender]

Hi,

My students (working with the matrix, i.e., 800+ types dumped
into their laps) have wondered whether it's possible to get the
LKB to identify the minimal type for which a feature is appropriate
(the type where the feature is declared).  I couldn't find 
any function that already does this, so I wrote a little utility.
I'm curious before I check it in though: does something else
already exist?  

On a similar note, it appears that my utility would be more
efficient if I had access to a topological order of the type
hierarchy.  Do we already have something that does this?

Thanks,
Emily