MFC:
fix what appears to me to be absolutle bogus code
to do with netmasks.. we fed totally bogus data into the kernel
to do with default routes and it just believed us. This led to:
1/ kernel panics
2/ the default route refusing to be deleted or added
(depending on a number of factors, usually it worked ok.)
I've test this all I can and it should stop panicing the kernel..
Never feed a sockaddr to the kernel without filling in the length
(and preferably the family).
The kernel is about to enforce this (again) so (this time) let's
get the user programs working first.