tor-proto: Make HopNum indices appear 1-based in the Display impl.
This makes HopNum
s display as 1-indexed values. This will make error
messages more intuitive, because when talking about an N-hop circuit, we
generally speak in terms of hops 1..N (rather than 0..N-1).
Internally, our HopNum
indices are still 0-based.
Closes #996 (closed)