GetLOS
Implement the GetLOS script instruction (with GetLineOfSight as an alias). This should be implemented via a new function in MWWorld::World.
Not sure if Invisibility/Chameleon magic effects come into play here. Needs to be checked.
(RM-758 from redmine: created on 2013-05-03 by Marc Zinnschlag, , closed on 2013-11-19 by gus gus)