Added 0-RTT support to TLS handshake in folly

[Anirudha Pratap Singh]

An OpenSSL solution for 0-RTT support in TLS handshake is added in folly's asyncSSLSocket API.

The following is the pull request: https://github.com/facebook/folly/pull/1369

With the above changes, a server application using AsyncSSLSockets can receive and process early data. The early data received as part of TLS clientHello can be parsed and based on it can be accepted or rejected. This solution is implemented using OpenSSL API SSL_read_early_data().

Can anyone please review the above feature request?

Thanks,

Anirudha