Initial OpenSSL BIO implementation, to be used to limit socket I/O

Initial OpenSSL BIO implementation, to be used to limit socket I/O
and remember raw data during peek phase of Peek and Splice.

No buffering yet: All SSL read/write commands go directly to the socket,
which probably creates some performance overhead because they use very
small I/O sizes (often just a few bytes).

Useful SSL connection state and I/O debugging.

Moved SSL connection creation and I/O association code into new Ssl::Create(),
used by client_side.cc and forward.cc.