ITS#5211 spec says we must ignore invalid cookies

Fix paged results control handling

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.

ITS#5072
ITS#5168

error message propagation fix

ITS#5127