bug when using SMTP module

The invite code use's PHP's "mail" function to send the invite. When the SMTP module is also installed, this results in the message not being sent (if sendmail is not enabled on the server). The solution is to use the drupal user_mail function instead in the _invite_send_invite function:

case "mail":
  //if ($success = mail($email, $subject, wordwrap($body, 72), "From: $from\r\nReply-To: $replyto")) {
  if ($success = user_mail($email, $subject, wordwrap($body, 72), "From: $from\r\nReply-To: $replyto")) {
    drupal_set_message(t('Your invitation was sent successfully.'));
  }