back_sql: default has_children_query does not work with oracle (ITS#2642)

[emmanuel.duru@atosorigin.com]

Full_Name: Emmanuel Duru
Version: 2.2.0 alpha
OS: solaris 8
URL: 
Submission from: (NULL) (195.68.44.148)


default has_children_query should be changed from SELECT ... FROM ldap_entries,
ldap_entries AS subordinates to SELECT ... FROM ldap_entries, ldap_entries
subordinates (just remove the AS keyword) because the first form works with
MySQL and not with oracle, whether the second form works with both.