OpenLDAP 2.6.4

This is a workaround for a possible bug in gcc when building optimized.
See: https://lists.openldap.org/hyperkitty/list/openldap-technical@openldap.org/message/QJE2LFXKQFDPHSBKNU5VLGIY57D6BV4X/
If it gets fixed in gcc we can remove the -fno-strict-aliasing

We can't rlock if we've registered ourselves as a writer. We can only
figure that out by checking if we're the thread that initiated the
pause: is the server paused already?

We're in a much better place now and there is only a single task active
for a given syncinfo_t plus the task that's just scheduled it and is
wrapping up. Any remaining times this wouldn't be true are probably bugs
to be fixed.

epoch_append should be called at the point the object is not reachable
anymore, otherwise a thread from a "future" might still access it post
reclamation.

Use cn=config format of TRUE/FALSE instead of slapd.conf format on/off

Same as ITS#9358 but for ordering matching rule, not just equality