old syntax for watchdog() call

The watchdog() call at line 893 of uc_payflowpro.module is still using the D5 syntax, and needs to be corrected to something like:

  if (!$curl_response) {
    watchdog('uc_payflowpro', 'Connecting to PayFlow server failed: %error', array('%error' => curl_error($ch)), WATCHDOG_ERROR, NULL);
  }