Add TLSv1.3 support
    
    Starting with NSS 3.28, TLS 1.3 support is available in upstream. TLS
    1.3 needs both a new configuration constant and a set of new ciphers.
    The latest version of TLS does not have any cipher suites in common with
    TLS 1.2 and older.
    
    The patch is based on initial work by Franziskus.
    
    https://pagure.io/mod_nss/issue/27
    
    Signed-off-by: Christian Heimes <cheimes@redhat.com>