Fixed PropDivXYZ isEntailed.

Fixed the isEntailed method. For example, the following code will return one incorrect solution.

```java
public static void main(String[] args) {
    Solver solver = new Solver();
    IntVar i = VF.enumerated("i", 0, 2, solver);
    solver.post(ICF.eucl_div(i, VF.one(solver), VF.zero(solver)).getOpposite());
    if (solver.findSolution()) {
        do {
            System.out.println(i + " / 1 != 0");
            System.out.println(solver.isSatisfied());
        } while (solver.nextSolution());
    }
}
```