Test server-side renegotiation.

This change adds support to the Go code for renegotiation as a client,
meaning that we can test BoringSSL's renegotiation as a server.

Change-Id: Iaa9fb1a6022c51023bce36c47d4ef7abee74344b
Reviewed-on: https://boringssl-review.googlesource.com/2082
Reviewed-by: Adam Langley <agl@google.com>
9 files changed