Includes Proto callable ``boost::proto::functional::size``.

A PolymorphicFunctionObject type that invokes the `boost::size()` function on its arguments.

A PolymorphicFunctionObject type that invokes the `boost::size()` function on its arguments.

`proto::callable`
This(Range)
boost::range_size< typename boost::remove_reference<Range>::type >
typename boost::range_size< Range const >::type `Range const &`

`boost::size(rng)`