Update NT build.

common controls across all tools.

the backend attempts a ldap_unbind() that results in calling
ldap_pvt_sasl_mutex_lock() with a NULL argument, causing a SIGSEGV.
I added a few assert() to catch this (I wonder if this might
be related to ITS#1982 "kill -INT corrupts database").

allowed per LDAP* handle. It works, but needs review.

  to back-bdb, back-ldbm and back-sql (the latter with limitations);
- added handling of ":dn" attributes to extended rfc2254 filters
  and to matched value filter
- altered the behavior of get_mra() when a matching rule is given:
  now it checks whether it is compatible with the attribute syntax
  and, in case it is, the given mr is used.  In case of no type,
  the check is delayed when filtering

retry partial writes

but see diff -r1.6 -r1.7 and it's obvious.)