RFR : 8016446 : (m) Add override forEach/replaceAll to HashMap, Hashtable, IdentityHashMap, WeakHashMap, TreeMap

[Mike Duigou]

Hello all;

This patch adds optimized implementations of Map.forEach and Map.replaceAll to 
HashMap, Hashtable, IdentityHashMap, WeakHashMap, TreeMap

http://cr.openjdk.java.net/~mduigou/JDK-8016446/0/webrev/

The implementations traverse the map more efficiently than the default iterator 
implementation and sometimes avoid creation of transient Map.Entry instances. 
The fast-fail behaviour of the default implementation is retained. 

Mike