#2 MiniX solver problem

[Andy Stevens]

The MiniX solver doesn't notice realise when there's
only one square on a diagonal where a digit can be
placed. e.g. a "1" in (5,2) and (3,5) rules out
placing one in every square of the diagonal except
(1,4), but clicking the "Hint" button doesn't find
this. Likewise for the mirror image, so both diagonals
have the problem.