By Morten S. Mikkelsen; this adds support for tangent bump shading

left: legacy bump, righ: sparkybump

http://pasteall.org/pic/show.php?id=13875

bugs [#26320], [#27506]

there's still an issue with texture OSA as you can see

source/blender/render/intern/source/render_texture.c

@@ -2620,6 +2620,12 @@ void do_material_tex(ShadeInput *shi)
 			}
 		}
 	}
+	if ((use_compat_bump || use_ntap_bump) && (shi->mat->mode & MA_TANGENT_V)!=0) {
+		const float fnegdot = -dot_v3v3(shi->vn, shi->tang);
+		// apply Gram-Schmidt projection
+		madd_v3_v3fl(shi->tang,  shi->vn, fnegdot);
+		normalize_v3(shi->tang);
+	}
 }