[PATCH v2 0/3] MR3419: wined3d: Implement a zero-safe normalize function for FFP

[Petrichor Park (＠petrathekat)]

DirectX's FFP normalizes the zero vector to the zero vector, but GLSL
normalizes them to all NaN.

This patch creates `ffp_normalize`, which normalizes vectors but
has DirectX's behavior on 0 vectors. Further patches in this set switch
other calls from GLSL's `normalize` to the 0-safe version.

This fixes [36564](https://bugs.winehq.org/show_bug.cgi?id=36564).

--
  v2: wined3d: Use ffp_normalize in shader_glsl_ffp_vertex_lighting_footer.
      wined3d: Use ffp_normalize in shader_glsl_ffp_vertex_lighting.
      wined3d: Implement a zero-safe normalize function for FFP.

https://gitlab.winehq.org/wine/wine/-/merge_requests/3419