color conversion: avoid type punning by returning SColor4ub directly. that required a non-extern-C declaration of the SSE function, so i replaced it with straightforward intrinsics.

ia32: no longer needs #if since build system ensures it's not compiled
on amd64

This was SVN commit r6164.

source/renderer/PatchRData.cpp

@@ -376,7 +376,7 @@ void CPatchRData::BuildVertices()
 
 			RGBColor diffuse;
 			lightEnv.EvaluateDirect(normal, diffuse);
-			*(u32*)&vertices[v].m_DiffuseColor = ConvertRGBColorTo4ub(diffuse);
+			vertices[v].m_DiffuseColor = ConvertRGBColorTo4ub(diffuse);
 		}
 	}