gtk/print.go
func (ps *PrintSettings) Set(key, value string) {
	cKey := C.CString(key)
	defer C.free(unsafe.Pointer(cKey))
	cValue := C.CString(value)
	defer C.free(unsafe.Pointer(cValue))
	C.gtk_print_settings_set(ps.native(), (*C.gchar)(cKey), (*C.gchar)(cValue))
}
func (ps *PrintSettings) Set(key, value string) {
	cKey := C.CString(key)
	defer C.free(unsafe.Pointer(cKey))
	cValue := C.CString(value)
	defer C.free(unsafe.Pointer(cValue))
	C.gtk_print_settings_set(ps.native(), (*C.gchar)(cKey), (*C.gchar)(cValue))
}
// Set() is a wrapper around gtk_print_settings_set().
// TODO: Since value can't be nil, we can't unset values here.