Fixed challenge header checking in nua/nua_stack.c when receiving 401/407.

Now checking for Proxy-Authenticate header when receiving 407 and
WWW-Authenticate header when receiving 401.

darcs-hash:20051020173953-65a35-78f63affe9d9175bc337c1ff8a362ae441438e93.gz

libsofia-sip-ua/nua/nua_stack.c

@@ -3031,8 +3031,8 @@ int crequest_check_restart(nua_handle_t *nh,
     }
   }
   else if (method != sip_method_ack && method != sip_method_cancel &&
-	   (status == 401 || status == 407) && 
-	   (sip->sip_proxy_authenticate || sip->sip_www_authenticate)) {
+	   ((status == 401 && sip->sip_www_authenticate) ||
+	    (status == 407 && sip->sip_proxy_authenticate))) {
     sip_t *rsip;
     int done;