Derive Macro AdtInto

#[derive(AdtInto)]
{
    // Attributes available to this derive:
    #[map]
    #[from]
    #[custom_arm]
    #[disable_mapping]
    #[use_field]
    #[prepend]
    #[append]
    #[args]
    #[todo]
    #[not_in_source]
    #[value]
}

AdtInto derives a SInto instance. This helps at transporting a algebraic data type A to another ADT B when A and B shares a lot of structure.