Add damaging "healing item" support
More tweaks/updates

Move player::cauterize to an iuse function
Give first aid a PKILL effect (from the recipe aspirin)
Make further bites on an infected/bitten limb increase effects
Cauterizing now will either remove a bite wound or greatly increase it's
effects
Cauterizing now causes 2 damage to the cauterized limb
Added some new player::functions to convert from hp_part to bp_part and
back again
Fix cauterizing for fun