rules: more graceful handling of anomalies for stable versions
Recent content hex notation fixes and xbits noalert fixes are causing upgrade issues for MSSPs that allow ppl to bring their own rules. In these cases the rules suddenly fail to load after Suricata has been upgraded, leading to confusion.
The fixes themselves were correct, perhaps we can default to a more graceful way of handling them, like with our classtype keyword.
This will need subtickets for the xbits and content cases when we agree on an approach