Security fix, CVE-2017-14495, OOM in DNS response
     creation.
    
        Fix out-of-memory Dos vulnerability. An attacker which can
        send malicious DNS queries to dnsmasq can trigger memory
        allocations in the add_pseudoheader function
        The allocated memory is never freed which leads to a DoS
        through memory exhaustion. dnsmasq is vulnerable only
        if one of the following option is specified:
        --add-mac, --add-cpe-id or --add-subnet.
    
    Signed-off-by: Petr Menšík <pemensik@redhat.com>