cryptui: add CryptUIWizDigitalSign stub

[Dmitry Timoshkov]

Vincent Povirk <madewokherd at gmail.com> wrote:

> This was surprising to me as well, but apparently we are using long
> for HWND in spec files.
> 
> It'd be nice to hear about why we do this (and why it's safe for us to
> do this) when HWND is a pointer-sized type, instead of a repeated
> assertion of "this is wrong", when it was a reasonable thing for
> someone unaware of this rule to expect. I have some guesses, but I'd
> rather hear from someone who knows about it.

Because window handles (and other user32 objects as well) are not pointers
by theire nature. Microsoft has invented a way to distiguish various handles
at compile time using a trick with defining a pointer to a dummy structure,
but once again that has nothing to do with real handles meaning.

-- 
Dmitry.