Macro add_bitflags

macro_rules! add_bitflags {
    ($STRUCT:ident,) => { ... };
    (
        $STRUCT:ident,
        $(#[$attr:meta])*
        Values {
            $($tt:tt)*
        },

        $($rest:tt)*
    ) => { ... };
}

rustfmt-friendly version of bitflags!.