Limit number of unprocessed syncrepl events in queue to 100.
    
    All syncrepl events are processed sequentialy. This patch limits
    memory consumption in cases where the LDAP server is sending
    syncrepl events too quickly.
    
    LDAP client library should handle this situation so no events
    will be lost.
    
    Signed-off-by: Petr Spacek <pspacek@redhat.com>