mmdevapi: IsFormatSupported fills closest match iff it returns S_FALSE.

Hi,

what about this patch of mine? #77305 is about to fall off the queue.
3 weeks later, it's still ok AFAICT.
> This will need another sweep in some future after somebody tests what happens
> in EXCLUSIVE mode about which MSDN says the pointer is set to null.
> I only tested SHARED mode with standard formats.

I've 2 patches in my queue that depend on this one:
- indeed, no format suggestion in exclusive mode;
- if all else fails, suggest GetFormatMix in shared mode

BTW, #77096 was superseded by something long committed.

Regards,
 Jörg Höhle