Expose NPN in OpenSSL.

This is derived from costin's change Ib18da136cb628515d6909c438cd0809452d7058a.
It moves the protocols data to the AppData's callbacks so the memory can be
released when the handshake completes.

Change-Id: Id61feaa6f28250e393f5c8093688b099e92dce9c
4 files changed