widl: added dispinterface and coclass

[Mike Hearn]

Robert Shearman wrote:
> This has nothing to do with proxy/stub marshalling. It is a step towards 
> type library generation though.

Hmm, I don't follow. Widl needs to be able to generate the NDR calls for 
the proxy/stubs. I've seen some work done on this lately, and was 
wondering how far this work has come. Widl needs to be able to do 
typelibs and old-style C marshallers, as IIRC some of the core COM 
interfaces can't be represented by type libraries.

thanks -mike