Fill in the missing documentation on the new functions

static char *consensus_join_lines(const smartlist_t *inp);

/** DOCDOC */

/** Compute the digest of <b>cons</b>, and store the result in

 * <b>digest_out</b>. Return 0 on success, -1 on failure. */

/* This is a separate, mockable function so that we can override it when

 * fuzzing. */

MOCK_IMPL(STATIC int,

consensus_compute_digest,(const char *cons,

                          consensus_digest_t *digest_out))

  return r;

}

/** DOCDOC */

/** Return true iff <b>d1</b> and <b>d2</b> contain the same digest */

/* This is a separate, mockable function so that we can override it when

 * fuzzing. */

MOCK_IMPL(STATIC int,

consensus_digest_eq,(const uint8_t *d1,

                     const uint8_t *d2))

  return cons2_str;

}

/**DOCDOC*/

/**

 * Helper: For every NL-terminated line in <b>s</b>, add a copy of that line

 * (without trailing newline) to <b>out</b>.  Return -1 if there are any

 * non-NL terminated lines; 0 otherwise.

 *

 * Unlike smartlist_split_string, this function avoids ambiguity on its

 * handling of a final line that isn't NL-terminated.

 */

static int

consensus_split_lines(smartlist_t *out, const char *s)

{

  return 0;

}

/** DOCDOC */

/** Given a list of lines, return a newly allocated string containing

 * all of the lines, terminated with NL, concatenated.

 *

 * Unlike smartlist_join_strings(), avoids lossy operations on empty

 * lists.  */

static char *

consensus_join_lines(const smartlist_t *inp)

{

  return result;

}

/**DOCDOC */

/** Given two consensus documents, try to compute a diff between them.  On

 * success, retun a newly allocated string containing that diff.  On failure,

 * return NULL. */

char *

consensus_diff_generate(const char *cons1,

                        const char *cons2)

  return result;

}

/** DOCDOC */

/** Given a consensus document and a diff, try to apply the diff to the

 * consensus.  On success return a newly allocated string containing the new

 * consensus.  On failure, return NULL. */

char *

consensus_diff_apply(const char *consensus,

                     const char *diff)