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.

with $EGREP_CMD from configure.  (Renamed from configure's $EGREP just
in case egrep variants exist that use the EGREP environment variable.)

Do not use test -a/-o.  Use shell features like &&, || or case...esac.
Use grep instead of egrep (but not the not-yet-portable Posix variant grep -E).
Based on a patch from Paul Eggert.

to "default", can be set to "accesslog" or "changelog". changelog is
not fully implemented yet.

only used for logging (c.f. accesslog overlay) the present phase is useless.

AttributeDescriptions must never be freed in a running slapd.