Add support for "vrrp" protocol keyword in Juniper firewall filters

[jathanism]

Currently the ACL parser only supports the numeric form (112) to specify vrrp as a protocol. Example:

term permit-vrrp {
            from {
                destination-address {
                    224.0.0.18/32;
                }
                protocol vrrp;
            }
            then accept;
        }
}

Enhance the parser to support either form. This was explicitly disabled in the past because it breaks parsing of certain Cisco access-lists. We can find a way!