The group list was being managed as an array of Group. This was

extremely broken and I can only wonder how I got some much mileage out
of it.  The problem is that we deal with pointers to the groups
themselves, either in current_group or current_to and current_nto.
These pointers would break on reallocs.  So now the the basic togroups
is an array to pointers to Group.  Since the array can be resized at
any time, what we actually pass around is pointer to an array of
pointers to Group or Group ***.