use upstream (sudo.ws) sudo, remove ldap dependency

this commit changes the default sudo installation to
upstream (www.sudo.ws).

This also removes the dependency on ldap, as there are upstream packages
without ldap support.

the perzl.org package is ok, but i think it's better to use the upstream
version. we are also going to change the sudo installation to sudo.ws on
our AIX systems.
Merge pull request #50 from tosmi/aixsudo

use upstream (sudo.ws) sudo, remove ldap dependency