rem: is_handler_allowed(T& handler, PPP_STATE state, PPP_PHASE phase)
add: is_handler_allowed(T& handler, ppp_state state, ppp_phase phase)
context: is_handler_allowed(T& handler, PPP_STATE state, PPP_PHASE phase){	if(handler.Protocol() == PPP_LCP_PROTOCOL)		return true;	else if(state != PPP_OPENED_STATE)		return false;	else if(phase > PPP_AUTHENTICATION_PHASE			|| (phase >= PPP_ESTABLISHMENT_PHASE				&& handler.Flags() & PPP_ALWAYS_ALLOWED))		return true;	else		return false;}