benefits of using a newer compiler, yay!
Explanation: the Link<...> template combines
various policy templates and exposes a set
of functions, which can be bound as functor
into an concrete time::Control instance.
Actually, we need to mix in only the Mutation
baseclass, because we just want to inherit
the privilege to change time values, which
are otherwise immutable. We don't need to
mix in the Mutator template anymore (this
was a leftover from an earlier design)
removed that inheritance relation; it was a typical
example of abusing inheritance and violated the
Liscov substitution principle. It is sufficient
to allow promotion of an offset into a Duration.
Note: Duration is the time metric
