Test-only DTLS implementation in runner.go.

Run against openssl s_client and openssl s_server. This seems to work for a
start, although it may need to become cleverer to stress more of BoringSSL's
implementation for test purposes.

In particular, it assumes a reliable, in-order channel. And it requires that
the peer send handshake fragments in order. Retransmit and whatnot are not
implemented. The peer under test will be expected to handle a lossy channel,
but all loss in the channel will be controlled. MAC errors, etc., are fatal.

Change-Id: I329233cfb0994938fd012667ddf7c6a791ac7164
Reviewed-on: https://boringssl-review.googlesource.com/1390
Reviewed-by: Adam Langley <agl@google.com>
8 files changed