George Kadianakis authored Jun 27, 2013 and Nick Mathewson committed Aug 15, 2013

- Don't leak if a transport proxy sends us a TRANSPORT command more
  than once.

- Don't use smartlist_string_isin() in geoip_get_transport_history().
  (pointed out by Nick)

- Use the 'join' argument of smartlist_join_strings() instead of
  trying to write the separator on our own.
  (pointed out by Nick)

- Document 'ext_or_transport' a bit better.
  (pointed out by Nick)

- Be a bit more consistent with the types of the values of 'transport_counts'.
  (pointed out by Nick)