[crossfire] Crossfire Plugin System v2.0

[Nicolas Weeger]

While we're at it :)
* could we use names more explicit that EVENT_GDEATH and EVENT_GKILL?
I'd say EVENT_PLAYER_DEATH and EVENT_KILL, less confusing
* EVENT_GKILL takes *two* parameters (what was killed and by who), only
one is used in plugin. And parameters should be inverted imo, first what
was killed, then by who (seems logical to always send affected item
first, then what object affects it imo)

Ryo