RFR (3rd) 8009736: Comparator API cleanup

[Henry Jen]

Hi,

Thanks for all the reviewing, hopefully this would be the last round as
we addressed feedbacks.

Mostly the difference from last round is javadoc[1], the only code
change[2] is that we override the default method of
Comparator.reversed() for natural/reverse order comparator in
Collections and Comparators as Peter Levart suggested.

[1] http://hg.openjdk.java.net/lambda/lambda/jdk/rev/c78083093dab
[2] http://hg.openjdk.java.net/lambda/lambda/jdk/rev/85308d92a4d6

Cheers,
Henry