better implementation for ITS#4996 and docs (ldapsearch(1) only; need to duplicate in other tools man pages)

handle returns in ldappasswd(1) and ldapwhoami(1).  Likely needs to be
added to other ldap*(1) commands.

Purports to remove kbind, but adds a ldap_search_s() request.

Removed all occurrences of Slurpd. The only mention from now in will be in replication.sdf, under "Replacing Slurpd"

require that ldap_pvt_thread_t can be cast to u.long and is not wider.
ITS#5010: In ldap_X509dn2bv(), catch error return from ber_decode_oid().

Remove ldap_int_thread_ctx_t.ltc_next.al (active list) left over from rev 1.75.

allow host resolution via DNS SRV based on the DN portion of the URI if no host is provided (ITS#4996)