CPP12 — implementing local interfaces in C++

There seems to be only two choices:

1. Accept that changing interfaces to local breaks old code that implemented
POA interfaces using servants. Not wonderful, but I can live with it, since
the source code changes are evident and fixed in a straightforward fashion.

2. Try to come up with a scheme where local objects can be implemented either
by using LocalObject or by the traditional servant route. This is more
specification work, but cleaner, and I an live with it too.

While we are at it, we should make sure that any other CORBA 3.0 changes are
properly reflected in the C++ mapping as well.

see proposed resolution for issue #4160