fixed a bug that made optimization return wrong values

This bug occurs while maximizing an objective function made of a single
literal. In this case, the returned objective values was negated.

org.sat4j.csp/src/main/java/org/sat4j/csp/constraints3/ObjBuilder.java

@@ -95,12 +95,12 @@ public class ObjBuilder {
 			coeffs.push(BigInteger.valueOf(val));
 		}
 		final ObjectiveFunction obj = new ObjectiveFunction(literals, coeffs);
-//		obj.setCorrection(BigInteger.ONE);
 		return obj;
 	}
 
 	public void buildObjToMaximize(final String id, final XVarInteger x) {
 		final ObjectiveFunction obj = buildObjForVar(x).negate();
+		obj.setCorrectionFactor(BigInteger.ONE.negate());
 		addObjectiveFunction(obj);
 	}
 	
@@ -211,7 +211,6 @@ public class ObjBuilder {
 		}
 		if(min < 0) throw new UnsupportedOperationException("negative coeff");
 		final ObjectiveFunction obj = new ObjectiveFunction();
-//		obj.setCorrection(BigInteger.ONE);
 		final BigInteger step = BigInteger.valueOf(max+1);
 		BigInteger fact = BigInteger.ONE;
 		for(int i=xlist.length; i>=0; --i) {
@@ -227,7 +226,6 @@ public class ObjBuilder {
 	
 	private ObjectiveFunction buildExprObjToMinimize(String expr, boolean negate) {
 		final ObjectiveFunction obj = this.intensionEnc.encodeObj(expr);
-//		obj.setCorrection(BigInteger.ONE);
 		if(negate) {
 			obj.negate();
 			obj.setCorrectionFactor(BigInteger.ONE.negate());
@@ -237,7 +235,6 @@ public class ObjBuilder {
 
 	private ObjectiveFunction buildSumObjToMinimize(final XVarInteger[] xlist, final int[] xcoeffs) {
 		final ObjectiveFunction obj = new ObjectiveFunction();
-//		obj.setCorrection(BigInteger.ONE);
 		final int size = xlist.length;
 		for(int i=0; i<size; ++i) {
 			obj.add(buildObjForVar(xlist[i]).multiply(BigInteger.valueOf(xcoeffs[i])));