Merge Samba 3.0 pdb_ldap from 3.0 into HEAD, so as to allow idra to continue

Merge Samba 3.0 pdb_ldap from 3.0 into HEAD, so as to allow idra to continue
his IDMAP work.

This version also works properly (the HEAD version had suffered from bitrot),
and should be a good basis to change into the new IDMAP rules.

It also includes UTF8 conversions.

Included also are the schema changes, and a note about the now very old scripts
in examples/LDAP (they don't work for this, or even the previous schema).

Andrew Bartlett
(This used to be commit 38a8f2b23a12f6a964d447f7904dd722a1ca046c)