Compare against n_max_frags with <=, not <.

Compare against n_max_frags with <=, not <.

It would be legal to use < if n_max_frags was exactly equal to n/best
(in that case we would know that dividing a stick into that many
pieces could at best equal the existing best score), but not if it's
merely floor(n/best) since then we might have previously seen an
_uneven_ dissection of a stick into that many pieces, which could be
beaten by an even one.

Reinstates the ability to do 7 into 4 with score 5/3 instead of the
3/2 reported by the previous version.