(ITS#3550) 2.2 syncrepl consumer gets errors from 2.3 provider

[hyc@OpenLDAP.org]

Full_Name: Howard Chu
Version: 2.2.23
OS: Linux
URL: ftp://ftp.openldap.org/incoming/
Submission from: (NULL) (24.126.120.178)
Submitted by: hyc


Running the 2.2 syncrepl consumer against a 2.3 provider now produces error
messages about "entryDN" being an unrecognized attribute. This is a new
operational attribute added in 2.3. The failure causes all the received entries
to be ignored.

As a quick fix for my tests I just copied the definition from 2.3 into 2.2's
core.schema (but as a user attribute, otherwise it fails to load). We need to
provide a better solution for 2.2 otherwise migration will be unnecessarily
painful.