[MEDIUM] stats: don't use s->ana_state anymore

[MEDIUM] stats: don't use s->ana_state anymore

The stats handler used to store internal states in s->ana_state. Now
we only rely on si->st0 in which we can store as many states as we
have possible outputs. This cleans up the stats code a lot and makes
it more maintainable. It has also reduced code size by a few hundred
bytes.