wined3d: adjust glPolygonOffset size

[Henri Verbeet]

2009/12/27 Austin English <austinenglish at gmail.com>:
> See bug 18993. Original author is credited in patch (  Dorek Biglari ).
>
This doesn't look right from my understanding of the d3d9 depth bias
behaviour. Afaik D3DRS_SLOPESCALEDEPTHBIAS is a multiplication factor
for the maximum depth slope (i.e. difference in z-value over distance
for a polygon's vertices), just like in OpenGL. I attached an
alternative patch to the bug.