Fix comments of functions that return tor_snprintf

No code changes needed: in the places where we actually check the
return value of these functions, we handle it correctly.

src/common/address.c

@@ -564,8 +564,8 @@ tor_addr_parse_PTR_name(tor_addr_t *result, const char *address,
 
 /** Convert <b>addr</b> to an in-addr.arpa name or a .ip6.arpa name,
  * and store the result in the <b>outlen</b>-byte buffer at
- * <b>out</b>.  Return the number of chars written to <b>out</b>, not
- * including the trailing \0, on success. Returns -1 on failure. */
+ * <b>out</b>.  Returns a non-negative integer on success.
+ * Returns -1 on failure. */
 int
 tor_addr_to_PTR_name(char *out, size_t outlen,
                      const tor_addr_t *addr)
@@ -2051,7 +2051,8 @@ parse_port_range(const char *port, uint16_t *port_min_out,
 
 /** Given an IPv4 in_addr struct *<b>in</b> (in network order, as usual),
  *  write it as a string into the <b>buf_len</b>-byte buffer in
- *  <b>buf</b>.
+ *  <b>buf</b>. Returns a non-negative integer on success.
+ *  Returns -1 on failure.
  */
 int
 tor_inet_ntoa(const struct in_addr *in, char *buf, size_t buf_len)

src/common/util.c

@@ -1953,7 +1953,7 @@ parse_http_time(const char *date, struct tm *tm)
 
 /** Given an <b>interval</b> in seconds, try to write it to the
  * <b>out_len</b>-byte buffer in <b>out</b> in a human-readable form.
- * Return 0 on success, -1 on failure.
+ * Returns a non-negative integer on success, -1 on failure.
  */
 int
 format_time_interval(char *out, size_t out_len, long interval)