This was the first official release of Phoenix as first class Boost citizen.
As a consequence of the review of Phoenix V2 the internals got completely
rewritten. Therefore the internal extension mechanism is different.
composite<...>, as_composite<...> and compose are gone and
have been replaced. For an in depth discussion see the section Inside Phoenix
phoenix::function now supports function objects that implement the Boost.Result
Of protocol. This is a breaking change
Boilerplate macros to easily adapt already existing functions and function
Bind is not completely compatible