[Pull Request 561] Tangent space fixes--100% MikkTSpace sync in UE4!

Pull request:

Polycount discussion thread:

Compute normals, import normals, import normals and tangents are all working 100% correctly in my tests for static and skeletal meshes, as opposed to the previous 80% correctly for static meshes and 99% correctly for skeletal meshes. UE4 now matches other MikkTSpace renderers perfectly (e.g. Xnormal, Blender, Toolbag 2) and retains its ability to import tangents and binormals from Max and Maya if that’s what you’re into (although this can make sections of the normal map that are baked for one part of the mesh and then duplicated or mirrored to others not work as well.)

I updated the pull request with support for skeletal meshes today, courtesy of James O’Hare. Please tell me what still needs to be done to get this merged for 4.6. I’d like to help you guys get this merged soon, as this patch means artists can spend even less time fiddling with bakes and more time making great-looking art with more room for optimization and additional polygons due to the reduced vertex count you can get for static meshes.