func AddString(ih *iup.Ihandle, x string, y float64) {
cX := C.CString(x)
defer C.free(unsafe.Pointer(cX))
C.IupPPlotAddStr(ih.C(), cX, C.float(y))
}
func (h *IupPPlot) AddStr(x string, y float32) {
cx := iup.NewCS(x)
iup.FreeCS(cx)
C.IupPPlotAddStr(toNative(h), (*C.char)(cx), C.float(y))
}