I get "Anonymous types declared in an anonymous union are an extension" in icmpv6.h

[FederAndInk]

Here I get "Anonymous types declared in an anonymous union are an extension" when trying to be pedantic, it would be better to not rely on non-standard c++ :) this is the only issue I got with pedantic enabled.

https://github.com/mfontanini/libtins/blob/b7e61f4c76ac64053c9c4c9f8eadaabbe3a9381a/include/tins/icmpv6.h#L1507-L1551