[python-ldap] LDAP Sync (RFC 4533) support

[Michael Ströder]

Chris Mikkelson wrote:
> Patch attached.
> 
> Demo script also attached. It "mirrors" the DNs of entries
> matching a search into a dbm, and prints out its updates.

I'm currently testing your module ldap.syncrepl with a slightly modified demo
script. Especially I'm interested in refreshAndPersist mode. This seems to
work for Modify Requests performed in the provider.

But in case of Add, ModRDN and Delete Requests at least the demo does not
produce what I'd expect. But maybe it's just me. I will further test it.

Anyway I've committed your code (with small clean-ups) to CVS HEAD will
release this as experimental addition along with 2.4.4 since it does not
affect the rest of python-ldap and we'll see what progress this makes.

Ciao, Michael.