forEach on HashMap and IdentityHashMap, Re: Loose ends inventory

[Remi Forax]

It was not listed in Brian list, but we should provide an implementation 
of forEach for HashMap that avoid to create an Iterator,
HashMap is too common to not have it's dedicated implementation
(ArrayList by example has its own implementation of forEach).

There is also another implementation that should have a specific 
implementation IdentityHashMap because
entrySet() creates map entries on the fly so having a specific 
implementation that will not allocatin entries will improve performance
(a lot for big identity hashmap).

cheers,
Rémi