Instantiating a Box from another Box does not perform a deep copy

[shikaan]

The underlying corner still points at the original corner, yielding unexpected behaviours.

Actual Behaviour

Box a(1,2);
Box b(a);
// a and b have the same corner

Expected Behaviour

Box a(1,2);
Box b(a);
// a and b have equal corners, but not _the same_