CCmpVision's AlwaysVisible is broken

[vts]

For the rally points, it is necessary to be able to render their marker flags inside the FoW. This can be specified by setting the AlwaysVisible property of the Vision component to true. However, this currently has no effect, and entities with this property remain invisible in the FoW.

To reproduce:

• Edit templates/special/actor.xml and edit the AlwaysVisible property to true.
• Observe that no actors are visible in the FoW.

After a discussion with Philip on IRC it became clear that this is a feature that didn't get implemented when the LOS rendering code was rewritten, and that it will probably involve non-trivial changes to rendering code.