@Jerry: Please revert if your are not content with this.
'ldapsam:trusted and 'ldapsam:editposix' are described in the smb.conf manpage, too.
--- /dev/null
+<samba:parameter name="winbind:rpc only"
+ context="G"
+ type="string"
+ advanced="1" developer="0"
+ xmlns:samba="http://www.samba.org/samba/DTD/samba-doc">
+<description>
+
+ <para>
+ Setting this parameter to <value type="example">yes</value> forces
+ winbindd to use RPC instead of LDAP to retrieve information from Domain
+ Controllers.
+ </para>
+
+</description>
+<value type="default">no</value>
+</samba:parameter>