prop250: Sort commits in lexicographical order in votes

  /* In our vote we include every commitment in our permanent state. */

  state_commits = sr_state_get_commits();

  smartlist_t *state_commit_vote_lines = smartlist_new();

  DIGESTMAP_FOREACH(state_commits, key, const sr_commit_t *, commit) {

    char *line = get_vote_line_from_commit(commit, sr_state_get_phase());

    smartlist_add(chunks, line);

    smartlist_add(state_commit_vote_lines, line);

  } DIGESTMAP_FOREACH_END;

  /* Sort the commit strings by version (string, not numeric), algorithm,

   * and fingerprint. This makes sure the commit lines in votes are in a

   * recognisable, stable order. */

  smartlist_sort_strings(state_commit_vote_lines);

  /* Now add the sorted list of commits to the vote */

  smartlist_add_all(chunks, state_commit_vote_lines);

  smartlist_free(state_commit_vote_lines);

  /* Add the SRV value(s) if any. */

  {

    char *srv_lines = get_ns_str_from_sr_values(sr_state_get_previous_srv(),