This command works on the invoking character like 'heal', however, it is not
normally used in NPC scripts and will not work as expected there, but is used
all over in item scripts.

Unlike 'heal', which just alters hp/sp and doesn't do anything else at all, this
command also shows healing animations for potions and other stuff, checks
whether the potion was made by a famous alchemist and alters the amount healed,
etc, etc. Since which kind of effect is shown depends on what item was used,
using it in an NPC script will not have a desired effect.

There is also a nice example on using this with the 'rand' function, to give you
a random ammount of healing.

// This will heal anything thing from 100 to 150 HP and no SP
itemheal rand(100,150),0;