No need to exactly invert whatever value is returned, especially as the Javadoc says we only return -1, 0 or +1.
This fixes Findbugs complaint about checking compareTo with a specific value, as well as avoiding a multiplication.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/collections/trunk@1476850 13f79535-47bb-0310-9956-ffa450edef68