add special implementation for add

The special implementation does not need to allocate an array for the
varargs of addAll

primitiveCollections/src/main/java/org/lucares/collections/IntList.java

@@ -112,9 +112,10 @@ public class IntList {
 	 *            the value to add
 	 */
 	public void add(final int value) {
-		// TODO add a special implementation that does not
-		// need to allocate an array for the varargs of addAll
-		addAll(value);
+		ensureCapacity(1);
+
+		data[index] = value;
+		index++;
 	}
 
 	/**