Get empty 'virtual' hierarchies working.

Commit b5125b1099cf5cf12beb0520d5896b9a1d7850ae
was broken.

We didn't add empty .ALL hierarchies as needed;
we added empty (non-existant) hierarchies without
appended '.ALL', and didn't add the original
empty group we started with.

(What's more, gatherstats didn't even start any
more due to missing ex- and import of
&ParseHierarchies from NewsStats.pm.)

Fixes #52 (and some more breakage).

Signed-off-by: Thomas Hochstein <thh@inter.net>