Fix check test with multi-leg moves

Fix check test with multi-leg moves

The check test after a multi-leg move was still using the same kill
square in the opponent's reply, making it blind to King captures in
a second leg. So far we got away with that because the Shogi multi-leg
pieces also can reach all their potential victims in a single step,
but with engine-defined multi-leg moves there is no guarantee this
will always be the case.