FRANCO STRICKEN BY HEART AILMENT
Spanish Gen Francisco Franco has fallen seriously ill with heart ailment, setting off rumors that transfer of power to Prince Juan Carlos de Borbon is imminent; seriousness of 82-yrâold chief of state's illness is underlined by 2 visits from Premier Carlos Arias Navarro and gathering of Gen Franco's family, including Dr Christobal Martinez-Bordiu, Franco's son-in-law; illus (M)