Add ldap_pvt_thread_pool_pausing(): pause check for slapd without locking.

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.

this number tunable.)

enabled with LDAP_THREAD_DEBUG (cpp macro and environment variable):

Move any ldap_pvt_* definitions from ldap_int_thread.h to ldap_pvt_thread.h.
#define ldap_int_thread_equal/ldap_pvt_thread_equal instead of tpool.c:TID_EQ.
Define some ldap_debug_*_t types, and LDAP_UINTPTR_T, in ldap_int_thread.h.
ldap_int_thread.h/ldap_pvt_thread.h can now be included multiple times, giving
different results depending on whether libldap_r/ldap_thr_debug.h was included.
Add some cleanup and some preprocessor hacks.
#define LDAP_THREAD*_IMPLEMENTATION in libldap_r/*.c, used by ldap_thr_debug.h.
Add PTHREAD_MUTEX_ERRORCHECK/PTHREAD_MUTEX_ERRORCHECK_NP in thr_posix.c.

must be reset by the caller to clear out temp allocations etc.

use arbitrary context pointers.

all threads.