Add two scripts that manipulate man-refs.ent. add-manref.sh inserts a
new man page entity with the right format into the right place.
Revs. 1.82-1.84 of man-refs.ent are a good, although perhaps extreme,
example of what this is trying to prevent. check-manref.sh makes sure
that the entities in man-refs.ent are in the right order, which is
necessary for add-manref.sh to work properly.