Profile add to group asks confirmation for non-mailing-list groups

If a profile adds contacts to a group and double opt-in is enabled, each contact gets sent a confirmation email, even if the group isn't a mailing list. It checks this for groups selected in the "group(s)" field, but there's no check for the group that all respondents are added to.

I've attached a patch to CRM/Profile/Form.php that takes care of this.