Support for feature #983.

Provide support for icmvp4 and icmpv6 as well.  You can now use

alert icmpv4 and
alert icmpv6 as well, apart from the existing

alert icmp, which created a rule that applied to both icmpv4 and icmpv6.

https://buildbot.suricata-ids.org/builders/poona/builds/19