Pre-check-in warning

Hi all,
   I just wanted to warn various people that I was going to do a  
rather monolithic check in to cvs in a little bit.  Hopefully after  
this one, my changes should be in smaller and neater increments.

There's a few relatively large changes.  Most obvious to you will be  
that I've completely re-written hat-detect (and an EDT module to go  
behind it).  Hat-delta now works (although it'll probably stack  
overflow on larger programs, I've got plans for fixing that), and  
will be checked in too.

Other than that there are a few movements of bits of code.  Most  
notably from the old HatDetect, and from HatExplore, into separate  
modules that can be loaded from elsewhere.

Yell (relatively) fast if you have major objections to this.

Bob