In general, for Red Hat, you probably want to keep using the system LDAP
libraries for all the clients and only use the new libraries for the LDAP
server. You have to be careful about any clients that would get loaded
into the server's namespace (libnss-ldap is the most common possible
culprit, but I think Red Hat links it statically to avoid this) since
otherwise there will be conflicts. So basically you install the server
and its libraries in a different path and things will usually just work.
It would be very nice if the OpenLDAP libraries supported and used symbol
versioning to make this somewhat more robust.