CPP12 — Local interfaces issue 1

The current specification of the local mapping requires the
implementation to enforce the "localness" of the object. This was very
similar to the (old) java mapping. The inheritance heirarchy is as
follows

CORBA::LocalObject : CORBA::Object

abstract MyLocalObject : CORBA::Object

MyLocalObjectImpl : MyLocalObject, CORBA::LocalObject

The problem here is that there is no way for the ORB or the code
generators to enforce the last inheritance. And I am not even sure how
an ORB can detect the following case

MyLocalObjectImpl : MyLocalObject

which I suspect would be a very common error.

Proposal:

Fix the mapping to have the following heirarchy.

CORBA::LocalObject : CORBA::Object

abstract MyLocalObject : CORBA::LocalObject <===== Difference is here

MyLocalObjectImpl : MyLocalObject <== and here

Now an _is_a("IDL:omg.org/CORBA/LocalObject:1.0") is guaranteed to give
a correct answer and it is enforced by the IDL compilers.

This is also backward source compatible.

see issue #4160 (the proposed resolution rejects this suggestion)