remove all the debugging stuff I added for evaluating various dispatch
paths for the reassembled IP frames.
Experiment with a new mbuf flag that indicates the frame has been re-injected.

For now most of the same checks in ip_input() are done - it only affects
te top level IP packet counter and avoids altq checks.
* On recommendation from grehan@freebsd.org, use a #define for ingress/egress
  rather than constants.
* For hashing udp lite it'll be fine to pass in the protocol type and
  have the RSS layer just 2-tuple hash it.  That way it'll end up
  hopefully being hashed the same way that the NIC hashes it.