sti [2/2]: add stubs for the IStillImageW interface

[Alexandre Julliard]

Damjan Jovanovic <damjan.jov at gmail.com> writes:

> I'm pretty sure you do need a separate IUnknown interface if the
> object aggregates, which it does on Windows (tests will follow).
>
> IIRC msxml3 does the same in node.c ...

I think it's nicer with a single table, but the COM book apparently
recommends two, so I guess I'll just have to get used to it...

But please make the real one the main lpVtbl, and the inner unknown a
secondary one, that makes things easier to follow.

-- 
Alexandre Julliard
julliard at winehq.org