Trac Ticket #448 - Possible to set invalid macros in Macro ACIs
    
    https://fedorahosted.org/389/ticket/448
    
    Bug description: Syntax checking code in acl did not check the
    macro syntax. Thus, invalide macro such as ($bogus.description)
    could have been unexpectedly added.
    
    Fix description: This patch adds the checking code: If acl contains
    a keyword starting with "($" or "[$", only one of "($dn)", "[$dn]",
    or "($attr." is allowed.