HTTPS not only for auth for Clickatell

I suggest to use SSL not only for auth in the Clickatell module since it can be a problem when only HTTPS connections are allowed on firewall.
Moreover, since Clickatell supports this, it is better to use it for a higher level of confidentiality.

I modified lines 226-227 as the following in gateway_clickatell_http.inc :

225 if ($this->use_ssl) {
226 $this->base = "https://api.clickatell.com/http";
227 $this->base_s = $this->base;
228 }