Several IP level socket options may affect TCP.

After handling them in IP level ctloutput, pass them down to TCP
ctloutput.

We already have a hack to handle IPV6_USE_MIN_MTU. Leave it in place
for now, but comment out how it should be handled.

For IPv4 we are interested in IP_TOS and IP_TTL.

Reviewed by: rrs
Differential Revision: https://reviews.freebsd.org/D32655