replmd linked attributes: lazy parsing for trusted DNs

replmd linked attributes: lazy parsing for trusted DNs

If we know that links from the database are in sorted order (via the
replmd_private->sorted_links flag), we can avoid actually parsing them
until it is absolutely necessary.

In many cases we are adding a single link to a long list. The location
of the single link is found via a binary search, so we end up parsing
log(N) DNs instead of N.

Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>