* Switch from ldap_search_st() to ldap_search_ext_s(). The latter is not deprecated.

* Ignore the return value from ldap_search_ext_s() because it appears to be misleading.  Instead, check to see whether the search returned any results (null or not null).  This also fixes a potential memory leak resulting from ldap_search_ext_s() returning an error code but still populating the search results.