Resolved deadlock by passing target entry to be_group and using
this if dn same as bdn.  It might actually be safer to check
entry ids instead of dns.
Resolved bogus add to cache after failed acl check by deferring
cache add until after parent/acl checks have successful been
completed.
Eliminated race condition caused by concurrent adds
of same dn by adding 'li_add_mutex' around the critical section
of code (most of ldbm_back_add).
This code is preliminary and still needs significant testing.

Seems that calling pthread_exit() in the main (and only active)
thread does not cause the whole process to exit.  Very odd.
Anyways, as we want to whole process to exit, we should just exit
after joining with our other threads.
I've also removed dead code for detaching threads we join with.

mutex declaration should be moved from slapd/main.c to slapd/init.c
so we don't have ripple changes through slapd/tools.

Introduction of ldbm_datum_init().
Patch for non-NULL pointer test befor call to ldbm_datum_free().

add/merge as we now free strings agressively.  Improved debug
message to include name of missing required attribute and added
check for 'operational attributes'.  This check should be used
everywhere we need to test for operational attributes (add/modify).
Also, enabled schema checking for tests (and fixed resulting
problems by adjusting oc.conf).

make it to dn2entry_r().

Also, output UNKNOWN_PREFIX ('?') instead of writing a nul character
when the attribute prefix is unknown.

have not implemented ldap_get_ber_controls() helper function yet.

to after other suffix checks.