Game server/skill system: type 9 skill expirations are now handled independently of 'saved magic' (skills persisting beyond logout), so they now expire properly; fixes #173.
Game server/skill system: appropriate stealth skills are removed at the correct time (i.e. on move/on move/attack).
Game server/skill system: prevented using both stealth types ('dispel on attack' & 'dispel on move') at the same time.