Add support for IP_RECVTOS
A SmartOS LX user discovered our lack of support using an LX zone. See https://github.com/joyent/illumos-joyent/issues/330 for that user's specific problem.
This is a case where to fix it in LX requires getting it to work in illumos native zones first. Luckily, we have a place to start working our way out. See here:
for receive-ancillary-data infrastructure. We will need to at least one bit for the above socket options, maybe two if we wish to keep them disjoint (though there's no TOS in IPv6, and no TCLASS in IPv4).
While not a bite-sized, that there is this data structure to keep track of ancillary data bits, it might not be a "hard" one either.