SLAPI support is a pain

["Howard Chu" <hyc@symas.com>]

As I filed ITS#2747 it struck me that we'll be having to take SLAPI into
account in too many different places. It shouldn't be this way, this is going
to get out of hand fast. It would really be a good idea to identify all the
kinds of hooks we want to support for SLAPI and provide a single point of
access to them, so we don't have to worry about this kind of oversight down
the road.

Since my take on SLAPI plugins at this point is that they are always
associated with a particular backend, it makes sense to me to encapsulate
their invocation in a slapd overlay, so that the SLAPI code only intrudes
when it's actually configured by an admin.

Comments?

  -- Howard Chu
  Chief Architect, Symas Corp.       Director, Highland Sun
  http://www.symas.com               http://highlandsun.com/hyc
  Symas: Premier OpenSource Development and Support