frontend stuff moved into a database structure, essentially to allow overlays to be processed before database selection; passes all tests (ITS#3080)

result to client.

instead of getting a timestamp at the end. This makes it possible for
slurpd to sort the log later.

(slapi_x_XXX is still reserved for exported functions that are not part
of the SLAPI specification)

1) simultaneous operation of multiple active sync replication threads
2) cookie management for individual sync replication thread
   (include rid=%3d to the slapd cookie command line option (-c))

- context csn management for delete
- a later patch will take care of inconsistencies caused by
  interactions between outstanding search and scope-outs

- conf file processing udpate
- misc updates

- add "updatedn" to the replication specification
- return referral to update to the slave server

order to prevent the operation from being passed to the backend. It
need only return a non-zero error code.

consolidated into the Operation structure. All reply parameters
are consolidated into the new SlapReply structure. Most operations
now have identical call signatures... Changes are not #ifdef'd,
revert to -r NO_SLAP_OP_BLOCKS if necessary to back out.

Support search preop/rewrite/postop plugins for root DSE and subschema

failure

Rename internal slapi_XXX API to slapi_x_XXX
Always set result code/matched/error text in operation parameter block
to make available to postoperation plugins

behaviour:

1. Plugins never return LDAP result codes, instead they return a
   small integer (0 or -1, others for special cases)
2. Preoperation plugins can abort processing by returning a non-
   zero value to the frontend
3. Postoperation plugins never abort processing (all are called)
   and their return values are ignored

Connection, Operation and Backend structures.

Ensure that SLAPI_MODIFY_MODS is set to an array of LDAPMods.