Merge branch 'mdw/backoff'

Merge branch 'mdw/backoff'

* mdw/backoff:
  server/tests.at: Test key exchange and retransmit with a flaky network.
  server/tests.at: Add a retry loop in `COMMS_EPING'.
  proxy: Add a `drop' filter to randomly discard packets.
  server/keyexch.c: Randomized exponential retransmit backoff.
  server/keyexch.c: Use high-resolution `struct timeval' timers.
  server/{keyexch.c,keyset.c}: Eliminate `ks_tregen'.
  server/{keyexch.c,keyset.c}: Move timing parameters to tripe.h.

Conflicts:
	server/tests.at