When the value hint mode is active, keep it active.

* Ie. when a different value is pressed, the hint is now being shown for
  the new value instead of turning of the value hints.

src/apps/sudoku/SudokuView.cpp

@@ -890,7 +890,7 @@ SudokuView::MouseDown(BPoint where)
 			}
 
 			if (value + 1 != fValueHintValue)
-				_SetValueHintValue(~0UL);
+				_SetValueHintValue(value + 1);
 
 			if (wasCompleted != fField->IsValueCompleted(value + 1))
 				_InvalidateValue(value + 1, false, x, y);