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This adds the ability to use Application-Layer Protocol Negotiation
(ALPN) as both a client and a server. ALPN is essentially like Next
Protocol Negotiation (NPN) but negotiation is done in the clear. This
allows the use of other protocols on the same port (e.g., SPDY instead
of HTTP on port 80).

Although previously clients using NPN were able to use cut-through, the
new ALPN API does not provide for a way for a client to enable that
during a callback. So the only difference is that NPN clients can enable
SSL False Start while ALPN clients cannot currently.

Change-Id: I42ff70f3711e9cccaf754d189f76eeaa9db5f981