Macro impl_bytes_newtype 

macro_rules! impl_bytes_newtype {
    ($t:ident, $len:expr) => { ... };
}

Implements several traits for byte-based newtypes. Implements:

• std::fmt::LowerHex (implies hashes::hex::ToHex)
• std::fmt::Display
• std::str::FromStr
• hashes::hex::FromHex