Macro pci_bit_field

macro_rules! pci_bit_field {
    (
        $(
            $(#[$attr:meta])*
            $vis:vis struct $name:ident<$lifetime:lifetime> : $mode:ident $type:ty {
                $(
                    $(#[$elem_attr:meta])*
                    $elem_name:ident @ $elem_first_bit:literal$(--$elem_last_bit:literal)? :
                    $elem_mode:ident $($elem_type:ty)?
                ),* $(,)?
            }
        )*
    ) => { ... };
}

TODO: Document.