Slight n-queens benchmark speedup for Casio fx-4000P, fx-7000G, etc.

[xerxes]

Thank you for the nice optimization, but I'm afraid it's not possible to use it for the list, because
that would mean to retest many devices (not only the CASIOs) with the same optimization.
I've dissolved my collection in the meanwhle and so I'm not able to retest all of them.
I think it's not really a problem, because the old test code is sufficient enough for comparing
the relative speed for the same algorithm.