comparators with lifecycle

[Radim Kolar]

I plan to implement comparators with lifecycle and make them backward 
compatible.

plan:
create Class LifecycleComparator implements Comparator
after new instance of comparator is created then check if its subclass 
of LifecycleComparator and if yes, then invoke init/shutdown methods.

https://issues.apache.org/jira/browse/MAPREDUCE-4851

Do you think that it has some chances to get committed?