- Jack Zhang reported a problem with SMTP: we wrongly used multiple addresses

- Jack Zhang reported a problem with SMTP: we wrongly used multiple addresses
  in the same RCPT TO line, when they should be sent in separate single
  commands. I updated test case 802 to verify this.

- I also fixed a bad use of my_setopt_str() of CURLOPT_MAIL_RCPT in the curl
  tool which made it try to output it as string for the --libcurl feature
  which could lead to crashes.