CPP12 — Valuebox for object reference underspecified

The CORBA 2.3 C++ mapping for valueboxes (1.17.7.2) does not specify the
behavior of the constructors, assignment operator and _value modifier
method with respect to the object reference argument. These methods
clearly need to call _duplicate on their argument, since the valuebox
must manage its own memory.

Proposal:

Add the following paragraph just before the example in 1.17.7.2:

Value box classes for object reference maintain a private managed copy
of the object reference. The constructor, assignment operator and
_value modifier method for these classes call _duplicate on the object
reference argument, and the destructor calls CORBA::release on the boxed
reference.

see below