...which should ''basically work,'' since `std::array` is ''»tuple-like«'' —
BUT unfortunately it has a quite distinct template signature which does not fit
into the generic scheme of a product type.
Obviously we'd need a partial specialisation, but even re-implementing this
turns out to be damn hard, because there is no way to generate a builder method
with a suitable explicit type signature directly, because such a builder would
need to accept precisely N arguments of same type. This leads to a different
solution approach: we can introduce an ''adapter type'', which will be layered
on top of `std::array` and just expose the proper type signature so that the
existing Implementation can handle the array, relying on the tuple-protocol.
__Note__: this changeset adds a convenient pretty-printer for `std::array`,
based on the same forward-declaration trick employed recently for `lib::Several`.
You need to include 'lib/format-util.hpp' to actually use it.