This implements support for TLS certificates compressed per the IETF
draft draft-ietf-tls-certificate-compression-04.

Notes:
 * zlib support is untested on account of nothing using it.
 * `HelloChrome_70` will still refuse to handshake with `www.google.com`
   due to the lacking support for the Channel ID extension.
 * There is no way in either the zlib library nor the brotli library
   to limit memory consumption, so really bad things may happen.