[Swan-dev] heads up, the great spd scramble

[Andrew Cagney]

I'm about to change "spd" in struct connection to a pointer; that is from:
   struct spd_route spd;
to:
  struct spd_route *spd;
My motivation is to make the code generating a list of SPDs from
subnets simpler (I'm guessing the first spd was embedded in the
connection as a memory optimization).

This touches everything.

Since i'm there, and since this is going to make a mess, I'm going to
piggy pack two other changes:
- struct end -> struct spd_end
because struct end pretty much only contains SPD stuff
- spd.this -> spd.local + spd.that -> spd.remote
because this and that get used to refer to either end