Merge passdb from HEAD -> 3.0

Merge passdb from HEAD -> 3.0

The work here includes:
 - metze' set/changed patch, which avoids making changes to ldap on unmodified
attributes.

 - volker's group mapping in passdb patch

 - volker's samsync stuff
 - volkers SAMR changes.

 - mezte's connection caching patch

 - my recent changes (fix magic root check, ldap ssl)

Andrew Bartlett
(This used to be commit 2044d60bbe0043cdbb9aba931115672bde975d2f)