Add strict DN syntax enforcement option.
    
    The DN syntax has become more restrictive over time, and the
    current rules are quite strict. Strict adherence to the rules
    defined in RFC 4514, section 3, would likely cause some pain to
    client applications. Things such as spaces between the RDN
    components are not allowed, yet many people use them still since
    they were allowed in the previous specification outlined in RFC
    1779.
    
    To deal with the special circumstances around validation of the DN
    syntax, a configuration attribute is provided named
    nsslapd-dn-validate-strict. This configuration attribute will
    ensure that the value strictly adheres to the rules defined in RFC
    4514, section 3 if it is set to on. If it is set to off, the server
    will normalize the value before checking it for syntax violations.
    Our current normalization function was designed to handle DN values
    adhering to RFC 1779 or RFC 2253