Performance plumets when using very small time scales during beam hits

Most evident using the screencam script, if you go into slowmo while anything is getting hit with a beam your framerate will soon being dropping rapidly.

I went poking through the code and it looks to me like both beam_handle_collisions in beam.cpp and weapon_hit in weapons.cpp create(or can create in the case of piercing effects) particle effects sources for all colliding beams every time they're run. If that read of them is correct, then that seems a likely source of the issue, and also dangerous to performance in general for high framerate players. I also think they might BOTH be making effects for the same things, but I'm not so sure about that one.