client/gamelib: change return type of destroyGameLib to bool
client/gamelib: change return type of destroyGameLib to bool

Sometimes the client can't be shutdowned, so we should reflect it via a return code.
karolherbst/Gamekeeper-Framework,karolherbst/Gamekeeper-Framework,karolherbst/Gamekeeper-Framework,karolherbst/Gamekeeper-Framework