ldb: use ldb directly rather than via a copy

ldb: use ldb directly rather than via a copy

This avoids needing to manually sync the two files, which due to the
top level build must be API compatible at all times anyway.

The most important recent change was:

commit e3b76bd6205acfc1a89fbcab5d9588b32cb47b88
Author: Andrew Tridgell <tridge@samba.org>
Date:   Thu Jul 28 15:51:31 2011 +1000

    ldb: fixed a search expression parse bug

However, as we always control the search expression in the callers to
this code, no backport to other releases is required.

Andrew Bartlett