Macro s_no_extra_traits

macro_rules! s_no_extra_traits {
    ($(
        $(#[$attr:meta])*
        pub $t:ident $i:ident { $($field:tt)* }
    )*) => { ... };
    (it: $(#[$attr:meta])* pub union $i:ident { $($field:tt)* }) => { ... };
    (it: $(#[$attr:meta])* pub struct $i:ident { $($field:tt)* }) => { ... };
}

Implement Clone and Copy for a struct with no extra_traits feature.

Most items will prefer to use s.