There were changes to the netfilter hook API in 4.1 and 4.4 to account
for, but those were simple.  No hook params we rely on changed.

There was a minor change to the proc handler table conventions back in
2.6.33, but that wasn't a deal-breaker.  Anyway, "fixed".

Much more bizarre was an apparent proc_dointvec change.  Since some
kernel between Ubuntu 3.13 and Ubuntu 4.2, proc_dointvec's behavior
changed (well, *something* changed!).  Some of our ipod sysctls
("icmp_ipod_host" and "icmp_ipod_mask") are uint32ts, but we have been
using proc_dointvec to parse the values sent in from sysctl, probably
forever.  So of course we regularly have to send in large negative
values (i.e. 155.98.32.70, aka 0x9b622046, aka -1688068026).  At 3.13,
proc_dointvec was happy to parse the hex version of that.  At 4.2, it is
not happy to parse the hex, but it will parse decimal.  Well, we don't
supply decimal in rc.ipod, just hex, and I don't want to fix it...