using a welder with already damaged eyes no longer causes you to go blind
Conflicts:
	code/game/objects/items/weapons/tools.dm
Fixes #4306 (When a head goes into cryo storage during Rev, a random crewmember is chosen as a target instead.)

Conflicts:
	code/game/machinery/cryopod.dm
Discovered/fixed a division by zero error for standing on the supermatter core.
Fixes #3907
Telebaton now only stuns if it actually hits.
Changed world loop to all_objective loop in cryopod check. Added all_objective add/remove procs to datum/objective.

Conflicts:
	code/game/machinery/cryopod.dm
fixed unfinished merge