GameSys: Update ComponentHumanPlayerT::TraceCameraRay() to operate in the clip world, not the physics world.
The physics world instance on the client is problematic: Whereas physics objects
on the server are instantiated as "dynamic" physics objects, on the client they
actually had to be instantiated as "kinematic", but at this time aren't.
See ComponentPhysicsT::UpdateDependencies() for details.
As a result, physics objects on the client are, at this time, never properly
updated, so that the previous implementation of TraceCameraRay() could not
properly work. For example, firing with the AR rifle at the crate in map Kidney
found particles at the wrong positions once the crate had moved from its
(In fact, we should probably not instantiate a physics world instance on the
client in the first place! Except possibly for eye-candy effects, it's quite
useless there. TODO!)
The new implementation works with the clip world, which is properly updated on
the client and thus yields the expected results.
Also, performance turns out to be much better with the new implementation,
so that this change in fact fixes #74.