Several changes to improve separation of the LM object and its lifecycle: * Store in ss7_asp a pointer to a xua_layer_manager, which contains all implementation dependent information inside its priv pointer. * Add a new free_func field to the xua_layer_manager struct in order to be able to free it without knowing how it was allocated. * Get rid og the loglevel param, LOGL_DEBUG was always passed and that was actually an implementation specific detail of the default xua layer manager. * get rid of struct lm_fsm_priv, it's not needed since it acutally only contain an asp pointer which can be passed directly as fi->priv.
