Factors: Old Math::Prime::Util:all_factors not giving all factors.

Math::Prime::Util:all_factors version 0.26 (which we have in the dist.ini) had a different behavior from 0.34. So the tests failed. This should fix it.
Merge pull request #261 from duckduckgo/jag/bug/factor

Factors: Old Math::Prime::Util:all_factors not giving all factors.