Deal with restricted types in unions

A typical example of a union which we do not handle correctly is:

    typedef pce-id {
        type union {
            type binary {
                length 4;
            }
            type binary {
                length 16;
            }
        }
    }

These types are restricted and guaranteed not to overlap, but our current codegen rules silently squash them to a single field (first one wins, I think).

There are multiple approaches we could take, like squashing the definitions, but that would only serve to confuse users – in this particular case they would be better served by generating encapsulated types for member – i.e. similar to what we do for enumerations.

We need to figure out the naming here – as we cannot just take the 'binary' string – that would result in conflicting names. That naming clash needs to be figured out also for something like:

    typedef pce-id {
        type union {
            type enumeration {
                enum a;
            }
            type enumeration {
                enum b;
            }
        }
    }