Because GUIDs are, in fact, not globally unique on mangos, the actual
unique identifier is the GUID/instance ID pair of the Creature.
On Trinity Creatures in instances are assigned new GUIDs. This means that
the instance ID part is redundant but must be used anyway for consistency.
Instead of decrementing all their counters every time an event occurs,
only the counters of the bindings being executed will be decremented.
`_LuaTemporariesDied` is a small optimization to prevent unnecessary calls
to `UpdateTemporaryBindings`. It will only be called when a temporary
binding has run out of shots and needs to be cleaned up.
This allows you to register a handler to only fire N times.
Dynamic event handler binding/unbinding is now possible.
For backwards compatibility, if the number of shots is missing, the event
handler will never be removed from the event.
