EMI: Don't apply lighting to overworld actors

Overworld actors, e.g. the load/save menu should not use
lighting based on the lights of the current scene. This
fixes the bug that the screenshots of the load menu
were dimmed to various levels depending on the current scene.

The bug fix is implemented for OpenGL, TinyGL and OpenGL Shaders.

Since the display of the overworld actors does not work with OpenGL Shaders, the bug fix could not be verified for this renderer.