This matches the declaration with official documentation and fixes
the following two compiler errors in apitrace project.

d3d9trace.cpp:28469:59: error: invalid conversion from 'const DXVA2_ConfigPictureDecode*' to 'DXVA2_ConfigPictureDecode*' [-fpermissive]
d3d9trace.cpp:28194:65: error: invalid conversion from 'void*' to 'IUnknown*' [-fpermissive]
Signed-off-by: Biswapriyo Nath <nathbappai@gmail.com>

With the changes from 0b8db612.

With the changes from 9c8f8e71.

Signed-off-by: Nikolay Sivov <nsivov@codeweavers.com>

Check the content of the output buffer in addition to checking the
return value.
Also show that multibyte characters are not truncated when the output
buffer is too small.

wine_dbgstr_w() already quotes (and escapes) the string.