ITCR — Valuebox should also have swap support

For valueboxes the spec should also describe swap support, they are complete so they can support swap. To be added:

A namespace level swap and a specialization of std::swap<> must be provided to exchange the values of two valueboxes in an efficient matter.

Valueboxes should have swap support

The issue proposed the support of swap for valueboxes but valueboxes are valuetypes which are reference types which already have swap support, also the boxed type has swap support. It doesn't add any value to define swap support for valueboxes because that can't be used at all, it is the valuetype reference and the boxed type that can be swapped and they have already swap support