Unifdef SLAP_LIGHTWEIGHT_DISPATCHER
Use thread-specific data in pool_context()
Added native thread-specific data support
Concurrency tweaks:
  store conn->c_sd, don't use ber_sockbuf_ctrl to retrieve it.
  use per-thread free lists for operations, no mutexes needed.

  store conn->c_sd, don't use ber_sockbuf_ctrl to retrieve it.
  use per-thread free lists for operations, no mutexes needed.

  "ABANDON", "STARTTLS", "CANCEL", "WHOAMI", "PASSMOD", "EXT", "INTERM",
  "TLS established", SASL and Extended Response "RESULT".
In Statslog output "conn=xx fd=yy closed", append the reason in
  "()" unless client or server closed the connection after Unbind.
Still missing Statslog output from a number of failed requests.

improve usability of global ovrlays for write operations; may need to anticipate SLAPI accordingly.  More work needed for add (overlays need to understand they're global and call slap_mods2entry() explicitly)

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

failure in slap_op_free is possible)

misc other cleanup

the conn->c_pending_ops queue.

Fixed minor compile errors

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.