LDAPObject.search_ext()

[<mi...@st...>]

HI!

I've committed some changes to use OpenLDAP 2.x's ldap_search_ext() instead 
of ldap_search().

This enables the application to specify a client-side search limit when 
using method search_ext() or search_ext_s(). The latter is inconvenient 
since ldap.SIZE_LIMIT_EXCEEDED is raised when the search limit was exceeded. 
Use (still undocumented) class ldap.async.List instead.

This change is hidden in a back-ward compatible way in wrapper class 
ldap.ldapobject.LDAPObject. Old code should still work.

Please test!

Ciao, Michael