Ticket #346 - Slow ldapmodify operation time for large quantities of multi-valued attribute values
    
    Description: slapi_entry_add_value is used to add values for sorting,
    which did not pass the attribute syntax info and the fallback compare
    algorithm was used.  It sometimes different from the attribute syntax
    based sorting and failed to find out an attribute.  This patch passes
    an attribute syntax info for sorting.
    
    Plus, featuring slapi_berval_cmp for the fallback compare algorithm.
    It is closer to the syntax based sorting.
    
    https://fedorahosted.org/389/ticket/346
    
    Reviewed by rmeggins@redhat.com (Thank you, Rich!)