[10] RFR 8171826 Comparator.reverseOrder(c) mishandles singleton comparators

[Paul Sandoz]

Hi,

Please review this simple fix.

http://cr.openjdk.java.net/~psandoz/jdk10/JDK-8171826-comparator-equality/webrev/

The method Comparator<T> reverseOrder(Comparator<T> cmp) is updated to be a 
little smarter returning constant comparators for natural and reverse-natural.

Paul.