Make the reflection types a black list (these types use (or should use)
the tag 'size-xxx' in their struct definition.s
HIP, IPSECKEY, NSEC3, TSIG
All other types don't use reflection anymore.
* Return a pointer to the header when there is no rdata, this restores old
behavior. The rest of the conversion mostly hangs on getting size-hex
right, but then packStruct and packStructValue and the unpack variant
can be killed.
* Generate pack and unpack for all embedded types as well.
* Fix PrivateRRs, register an unpack function as well, when you register
a new PrivateRR.
* Add the tag octet, nsec, []domains and more to msg_helper.go