Tags: patch done

I'm afraid there are several problems in the dfa code.  I still don't 
have a handle on all of them, but here's my first patch to deal with the 
first major one I found.  Patterns like [a-[.z.]], which caused 'grep' 
to dump core until recently, still aren't being handled correctly, and 
there are several closely related bugs here.  I've taken the liberty of 
pushing the attached patch.