message: add helper to deserialise a Cbor object
diff: @@ -437,6 +437,12 @@ impl<'a> RawCbor<'a> {
  _ => unreachable!()
  }
  }
  +
  + pub fn deserialize<T>(&mut self) -> Result<T>
  + where T: Deserialize
  + {
  + Deserialize::deserialize(self)
  + }
  }
  impl<'a> From<&'a [u8]> for RawCbor<'a> {
  fn from(bytes: &'a [u8]) -> RawCbor<'a> { RawCbor(bytes) }
  