windowscodecs: Implement GetThumbnail in the ICO frame decoder.

[Dmitry Timoshkov]

Dmitry Timoshkov <dmitry at baikal.ru> wrote:

> It's still better to return WINCODEC_ERR_CODECNOTHUMBNAIL instead of
> E_INVALIDARG

E_INVALIDARG -> E_NOTIMPL

-- 
Dmitry.