allow worn welding goggles to be used in veh_interact.cpp
Remove non-functional nanosleep code that was lagging when flinging monsters.
Fixes #3848
Recategorization of waterskin and stone knife

Moves waterskin to Other -> Containers and stone knife to Other -> Tools.
Moved holographic sights to 'sights' slot
Fixed bug where removing a mod doesn't free the location slot.