Macro glib_newtype_display

macro_rules! glib_newtype_display {
    ($typ:ty) => { ... };
    ($typ:ty, Format::$format:ident) => { ... };
    ($typ:ty, $displayable_option_name:ident) => { ... };
    ($typ:ty, $displayable_option_name:ident, Format::$format:ident) => { ... };
}