cubicToQuadratic: store 'curve_type' in layer's lib
cubicToQuadratic: store 'curve_type' in layer's lib

but keep reading it off the global font's lib, for backward compatibility

googlefonts/ufo2ft,googlei18n/ufo2ft,jamesgk/ufo2ft,jamesgk/ufo2fdk,moyogo/ufo2ft