Having looked at Keen's clue selection code, I also notice that the

intended behaviour of classifying multiplication clues as low-quality
if they only left one possible pair of multiplicands has never
actually worked, because I should have compared the possible clue
count against 2 rather than 1 since the multiplicands can occur either
way round.

git-svn-id: svn://svn.tartarus.org/sgt/puzzles@9165 cda61777-01e9-0310-a592-d414129be87e