use normal specified by the user for lighting in world coordinates

lighting/v_shader.glsl

@@ -12,5 +12,5 @@ void main(void)
 {
     gl_Position = projection * modelview * vec4(pos, 1);
     pos_i = vec3(gl_Position.x, gl_Position.y, gl_Position.z);
-    normal_i = vec3(modelview * vec4(normal, 0.0));
+    normal_i = normal;
 }