The mechanism used to select algorithm implementations based on
sequence family has been changed to use metafunction classes:
| Before | Now | 
|---|
| name_traits<Tag>::algorithm<...>::type | name_impl<Tag>::apply<...>::type | 
If your code implemented a custom sequence, it needs to be adjusted
according to the above table; for example:
| Before | Now | 
|---|
| 
template<> struct begin_traits<my_tag>
{
    template< typename S > struct algorithm
    {
        typedef ... type;
    };
};
 | 
template<> struct begin_impl<my_tag>
{
    template< typename S > struct apply
    {
        typedef ... type;
    };
};
 |