HEADS UP: backend interface change

["Kurt D. Zeilenga" <Kurt@OpenLDAP.org>]

The Frontend/Backend interface has been redesigned to support better
startup and shutdown of services.  The interface now supports per
backend type (info) initialization, startup, shutdown, destroy entry points
as well as per database initialization, startup, shutdown, destroy
entry points.

Also, the bi_init (backend info) initializer is now responible for
installing callbacks.  The frontend needs only to know the type (ie: "ldbm"
and this one entry point.  This will facilate future support for dynamically
linkable backends.

The new interface is also allows for per backend type (info) configuration
options to be established.

Also, all entry points now return status.  This will allow implementation
of better fault handling.

For additional details on the changes, please see the commit log and 
comments in slapd, rev 1.30.

For those implementing backends, please use back-shell as an example.

	Kurt