[2/2] oleaut32: Implement a better stub for IPicture::SaveAsFile.

[Vincent Povirk]

> Failures in gdiplus tests are caused by broken code in gdiplus, in particular
> GdipCloneImage() is broken. First, it calls IPicture_SaveAsFile() with 'mem_copy'
> parameter set to FALSE, and according to the tests IPicture_SaveAsFile() always
> returns E_FAIL in that case. Second, IPicture_SaveAsFile() has never been writing
> correct data to the provided stream, so despite that it hasn't returned an error
> the result just couldn't be correct. It looks like whoever has written that code
> hasn't tested it at all.

Really, gdiplus code shouldn't be using IPicture at all. We should
instead use gdi32 metafile handles directly.