Fixing wrong prototypes in a header

[Juan Lang]

> I think that's a case where we could diverge from the PSDK (with a
> comment explaining why). Otherwise the header is completely useless: we
> could not even make sure its prototypes match those of our
> implementation.

Thanks Francois, I was hoping you'd check in.

> Btw, did you check this against the very latest PSDK?

Well, I checked against a PSDK I installed a month ago.  If there's a
newer one, I haven't checked it.

> Could you provide the name of one of these functions?

They're function pointers, actually.  All the function pointer members
of CRYPT_PROVIDER_FUNCTIONS in wintrust.h are declared without a
calling convention.  They need to be declared __stdcall.  Is the
default calling convention for VC++ __stdcall?  If so, that'd explain
the difference.

Thanks,
--Juan