HotSpot Style Guide should permit use of lambda

Lambda expressions are a new (in C++11) syntax for anonymous function objects. They are much more expressive than function object classes for many use-cases, particularly for small local functions. A simple function object class might require 1/2 dozen to a dozen LOC, much of which is ceremonial boiler plate. Such a class might often be replaced by 1-2 actually interesting LOC by using a lambda expression.