[Python-3000] multi-dispatch again

[Bill Janssen]

Of course, the purpose of using ABCs is to allow easy inspection of
the capabilities of an object, and for some objects, the state can be
an important part.  But don't be misled to confuse ABCs with simply
type-based function dispatch.  They're useful for other things as
well.

I think that stateful value types should probably have, as you say,
mechanisms for inspecting that state.  For instance, the current
"file" type has a "closed" attribute, doesn't it?

Bill