Fix aborted detour under-promotion XB

Fix aborted detour under-promotion XB

When a dragged Pawn was released before the promotion piece was fixed,
this would fake a release on the from-square. But the repair of animation
damage would take place on the to-square derived from the actual mouse
coordinates. When this was different from the from-square, the animation
damage (consisting of removalof the piece) would thus not be repaired
by redrawing that square, as normally (when the to-square is different)
it should remain empty. Now we mark the from-square as damaged when the
detour under-promotion changes the dragged piece.