tcp md5


There was very very old code in the kernel for tcp md5, from around 4.4BSD vintage. Never worked.

tcp md5 is somewhat similar to ipsec ah, so implement it within the IPsec maze

that unfortunately meant that I had to add a pfkey interface to bgpd. committee designed API...
lead to lots of head banging and beer

on the positive side, that made IPsec a lot easier
we extended the API so that we can request a pair of unused SPIs from the kernel, so they don't not have to be configured