Constant BASE32HEX_NOPAD

Unpadded base32hex encoding

This encoding is a static version of:

# use data_encoding::{Specification, BASE32HEX_NOPAD};
let mut spec = Specification::new();
spec.symbols.push_str("0123456789ABCDEFGHIJKLMNOPQRSTUV");
assert_eq!(BASE32HEX_NOPAD, spec.encoding().unwrap());