PR# 19980 Conversion procedures with the same feature name

When we have two conversion procedures of the form:

```eiffel
convert
    f ({CC}),
    f ({DD})
```

EiffelStudio reports a VNCP validity error complaining that routine `f` is specified twice in the convert clause. But there is nothing in the Eiffel standard which forbids this. It should be equivalent to:

```eiffel
convert
    f ({CC, DD})
```

--
Eric Bezault

class BB

create

	f

convert

	f ({CC}),
	f ({DD})

feature

	f (a: DD)
		do
		end

end
~~~~
class CC

inherit

	DD

end
~~~~
class DD

end