When reassembled IPv6 fragments are NATed or RDRed by pf, the checksum has to be recalculated before the packet is fragmented again.  Put a missing in6_proto_cksum_out() into pf_refragment6(). This makes run-regress-frag6 and run-regress-frag6-ext pass again. From Matthias Pitzl; OK henning@
When reassembled IPv6 fragments are NATed or RDRed by pf, the
checksum has to be recalculated before the packet is fragmented
again.  Put a missing in6_proto_cksum_out() into pf_refragment6().
This makes run-regress-frag6 and run-regress-frag6-ext pass again.
From Matthias Pitzl; OK henning@

orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars